Nouvelle Série, Tome XIV, Fasc. 3

1979

REVUE

ALGOLOGIQUE

Fondée en 1922 par P. ALLORGE et G. HAMEL

Directeurs : P. BOURRELLY et R. LAMI

Secrétariat de Rédaction : M. RICARD

SOMMAIRE

G. CLAUS. - Microstructures in meteorites, or fossilized ideas about

idéal fossils.1^7

C. ANDREIS. - Pores in the apical cell of Oscillatoria limosa Ag.235

V.S. SUNDARALINGA, A.K.S.K. PRASAD and S. SUBBALAKSHM1. -

Studies on South Indian soil algae : Gloeocystis gigas Collins (Tetraspo-

rales). . . ..

239

J.C. DRUART & O. REYMOND. - Paradoxia pelletieri, nov. sp. Nouvelle

espèce de Chlorococcales de France (Chlorophyceae).

M. CHADEFAUD. - L’évolution de la structure cladomienne chez les

Charales et les Céramiales. Étude comparative.

OUVRAGES REÇUS POUR ANALYSE

275

LES DIATOMEES LACUSTRES PLIO-PLEISTOCENES DU GADEB (ETHIOPIE)

SYSTEMATIQUE, PALEOECOLOGIE, BIOSTRATIGRAPHIE

par Françoise GASSE

(Ecole Normale Supérieure, 92260, Fontenay aux Roses, France)

210 pages, 62 planches, 150 références, broché.

Prix de souscription : 260 FF, parution : déc. 1979.

L’auteur étudie dans cet ouvrage les diatomées d’une séquence continentale, lacus¬

tre puis fluvio-lacustre, de 45 m d’épaisseur, d’âge plio-pléistocène (2.7-0.7 millions

d’années), récoltées sur les hauts plateaux volcaniques d’Ethiopie (2300 m d’altitude).

La première partie est consacrée à la description de la flore : 392 taxons apparte¬

nant à 31 genres ont été inventoriés. Cette étude taxinomique contient la description

de nombreux taxons nouveaux ou intéressants et s’appuie sur 62 planches photogra¬

phiques réalisées en microscopie photonique et électronique à balayage : près de 900

clichés représentant 265 taxons et leurs variations spécifiques.

Dans la deuxième partie, les associations successives des diatomées de la phase

franchement lacustre (2.71-2.35 millions d’années) sont définies et interprétées. Ces

associations sont très diversifiées et leur composition floristique s’explique par l’évolu¬

tion écologique du milieu et l’âge ancien des dépôts. Des fluctuations climatiques

globales paraissent, en partie, responsables des changements écologiques enregistrés par

les diatomées. L’ancienneté de la flore se manifeste principalement dans le groupe des

centriques [Melosira, Cyclotella, Stephanodiscus) et se traduit par l’abondance d’es¬

pèces éteintes ou d’aire biogéographique actuellement restreinte. Leur valeur bio-

stratigraphique est soulignée par l’analyse de leur paléogéographie et paléostratigraphie

mondiale. Certaines espèces vivant encore actuellement présentent des caractères

archaïques et l’existence de nombreuses formes intermédiaires reflète une période

d’intense évolution spécifique.

L’analyse des diatomées lacustres plio-pléistocènes du Gadeb est la première étude

d’une séquence épaisse, continue et très bien située dans le temps par de nombreuses

datations radiométriques. Seul, ce type d’étude permet des corrélations interrégionales

et intercontinentales pouvant apporter des conclusions générales sur l’évolution des

milieux continentaux, la paléobiogéographie et la phylogénie des diatomées. De plus,

la richesse et la qualité de l’illustration en font un important document sur la systé¬

matique et la biogéographie des diatomées lacustres plio-pléistocènes.

LES DIATOMEES LACUSTRES PLIO-PLEISTOCENES DU GADEB (ETHIOPIE)

SYSTEMATIQUE, PALEOECOLOGIE, BIOSTRATIGRAPHIE

par Françoise GASSE

BON DE RESERVATION

Ce bon de réservation est destiné à préciser le nombre de personnes intéressées par l’achat de

cet ouvrage. En juillet 1979, les personnes ayant renvoyé ce bon recevront un bon de commande

leur permettant d’acquérir ce livre au prix de souscription.

Nom :

Institution :

Adresse :

Renvoyez à : Revue Algologique, 12, rue de Buffon, 75005 Paris, France.

PLIO-PLEISTOCENE LACUSTRINE DIATOMS FROM THE GADEB (ETHIOPIA)

SYSTEMATIC, PALEOECOLOGY, BIOSTRATIGRAPHY

by Françoise GASSE

(Ecole Normale Supérieure, 92260 Fontenay aux Roses, France)

210 pages, 62 plates, 150 references, bound.

Subscription price : 260 FF, issue on Dec. 1979.

In this paper, the author présents the diatom study of a continental (lacustrine and

fluvio-lacustrine) sequence of 45 m thick and dated from 2.7 to 0.7 million years. The

geographical and geological setting of the sédiments, taken from the volcanic uplands

(2300-2350 m in élévation) of Ethiopia, is briefly described in the introduction.

The fîrst part is relative to the systematical study of the rich diatom flora : 392 taxa

belonging to 31 généra. This taxonomical chapter is based on 62 photographie plates

in photonic (28 plates) and scanning microscopy (34 plates). 265 of the taxa are

represented, taking into account their spécifie variations.

In the second part, the successive diatom assemblages of the entire typical lacus¬

trine phase (2.71-2.35 million years) are defined and interpreted. Their floristic com¬

position dépends on the ecological évolution of the biotope and on the Plio-Pleistoce-

ne âge of the deposits. Ecological changes deduced from the diatom flora seem to be

partly due to global climatic fluctuations. The âge of the flora appears clearly through

the Centric diatoms ( Melosira, Cyclotella, Stephanodiscus). It is registered by the

abundance of species now extinct or with today restricted biogeographical area.

The study of their paleogeographical distribution and their stratigraphie al range

throughout the world indicates they are excellent biostratigraphical markers. Many

species présent transitional forms indicating that the Plio-Pleistocene was a period of

intensive spécifie évolution.

The analysis of the plio-pleistocene lacustrine diatoms of the Gadeb represents the

flrst diatom study on a thick and continuous continental sequence set within a ra-

diometrically dated time scale. Only this type of study allows interregional and inter¬

continental corrélations and will lead to general conclusions concerning the ecological

évolution of the continents, the paleobiogeography and the phylogeny of the diatoms.

The numerous illustrations make this an important work for the systematic and the

biostratigraphy of the plio-pleistocene lacustrine diatoms.

PLIO-PLEISTOCENE LACUSTRINE DIATOMS FROM THE GADEB (ETHIOPIA)

SYSTEMATIC, PALEOECOLOGY, BIOSTRATIGRAPHY

par Françoise GASSE

RESERVATION FORM

This réservation form is designed to estimate the number of persons interested in buying

this book. In July, we will send you an order form with the subscription price.

Name :

Institution :

Address :

Return to : Revue Algologique, 12, rue de Buffon, 75005 Paris, France.

197

MICROSTRUCTURES IN METEORITES

or Fossilized Ideas About Idéal Fossils

George Claus*

RÉSUMÉ. — Les termes «éléments organisés» furent introduits en 1961 pour désigner des

microstructures, découvertes dans des météorites carbonées du Type 1, et censées représen¬

ter des restes de microfossiles. Bien que ces structures aient été facilement découvertes

dans les laboratoires où de telles météorites étaient examinées, différents chercheurs four¬

nirent des explications variées concernant leur nature et leur origine. Dans cet article sont

présentés les résultats des examens microscopiques électroniques à transmission et à ba¬

layage de fragments intacts de microstructures provenant de la météorite d’Orgueil. Ces

observations décrivent des éléments organisés intimement enrobés dans une matrice consti¬

tuée de roches, ce qui exclut totalement l’hypothèse d’une contamination pour expliquer

la présence de ces éléments. Ces éléments ont été analysés par diffraction aux rayons X et

les résultats obtenus indiquent que certains de ces corps contiennent du carbone ainsi

que des éléments minéraux. La discussion finale fait ressortir la difficulté de préciser l’ori¬

gine des fossiles précambriens et des microstructures météoritiques.

ABSTRACT. In 1961 the term «organized éléments» was introduced to designate indi-

genous microstructures discovered in Type I carbonaceous meteorites, which were believed

to represent remains of microfossilia. Although these structures were. easily found in labora-

tories where such meteorites were investigated, different researchers offered varied alter¬

native explanations as to their nature and origin. They were identified as minerai grains,

terrestrial contaminants, prebiological organic structures, or any combination of these.

Later extensive work has demonstrated that the question of terrestrial contamination had

been greatly overemphasized, and the claim that the majority of the organized éléments

are minerai grains is no longer asserted. The currently favored idea is that they are organic,

indigenous forms, but are the resuit of abiogenesis. Results of transmission and scanning

électron microscopie investigations on intact fragments of the Orgueil meteorite are presen-

ted, depicting organized éléments intimately embedded in the matrices of the stone, thus

excluding the possibility that these objects are contaminants. The elemental composition

of individual microstructures is defined with energy dispersive X-ray analysis, and it is

shown that some of the bodies, even after HF treatment, contain carbon as well as minerais,

the latter having elemental abundances comparable to those of the stone, attesting both

their organic and indigenous nature. Fine morphological characteristics of different types

* 1208 Tudor Court, Somerville, N. J. 08876 U.S.A.

Rev. Algol., N. S., 1979, XIV, 3: 197-233.

Source : MNHN, Paris

198

G.CLAUS

of structures are illustrated and described, and the question of their biogenic nature is rai-

sed. After discussing the various proposais for establishing the biogenecity of many early

Precambrian microfossils, it is concluded that unless new criteria are devised, it is equally

impossible to prove the vital origin of simple Precambrian fossils as that of the organic

meteoritic microstructures.

This paper has a threefold purpose : to recount the furor which erupted

after the suggestion was made that the organized éléments in carbonaceous

chondrites are indigenous microfossils; to présent results of ultrastructural

investigations which are not incompatible with the correctness of this inter¬

prétation; and to examine whether, within the framework of prevailing scienti-

fic dogmata, proof for this contention could be arrived at by any means.

INTRODUCTION

About 17 years ago to date, together with a colleague of mine, I published

a paper in the British scientific weekly Nature in which - having conducted

some investigations on two Type I carbonaceous chondrites, the Orgueil and

Ivuna meteorites - I had the temerity to propose that these bodies carry remains

of autochthonous microfossils of extraterrestrial origin (1). This statement

initiated an explosive controversy which has not yet been settled, at least not

to the satisfaction of ail parties concerned. The ensuing debate was often acri-

monious, and by the late 1960s it appeared advisable to let matters stand where

they were, and to temporarily withdraw from the battle.

In 1961, the idea of finding extinct life forms in certain meteorites did not

seem particularly strange to me; in fact, for a time I could hardly comprehend

the viciousness of many of the subséquent attacks, which I thought quite unwar-

ranted by the nature of our results. After ail, it had been known for close to

100 years that the Orgueil meteorite contains considérable quantities of organic

carbon compounds (about 5% by weight), and these had been identified by

CLOEZ as similar to terrestrial humâtes a few weeks after the stone fell, in

France, in 1864 (2, 3). The studies of BOATO (4) demonstrated that this

meteorite (and three others, known together as WIIK’sType 1 carbonaceous

chondrites (5, 6)) contains as much as 20% water, in the main of extraterrestrial

origin; and as it was accepted at that time, on the basis of the minerai suite

présent in the stone, that the parent body had had a low température, aqueous

environment (7, 8), there seemed to be but little difficulty in the interprétation

offered for the results of our microscopie studies. What I was not yet aware

of at that time was the fundamentally conservative nature of the scientific

endeavor itself - a factor frequently alluded to in historical or philosophical

analyses on the process of discovery (9, 11) - but which, as a practicing member

of the scientific community and also a curious member of the human race, I

could not accept. It happened, however, that the publication of our simple

MICROSTRUCTURES IN METEORITES

199

observational results had implications far beyond the assertion that micro-

fossils had been found in two meteorites : a number of cherished and well-

established hypothèses regarding the origin of life, of meteorites, and even

of the solar System would hâve had to be modifxed had these findings been

accepted.

In retrospect, it seems évident that one major obstacles to acceptance was

the purported history of the meteorites’ parent body. Since it is not the sub-

ject of this paper to review the divergent concepts about the parent body, it

should only be mentioned that meteorites are thought to originate in the belt

between Mars and Jupiter as a resuit of collisions among asteroids, the latter

representing the condensation products of primordial gases of the solar nebula

which never formed a planet. Carbonaceous chondrites are taken to be the most

primitive matter in the solar System, as they hâve supposedly undergone the

least amount of chemical fractionation since the time of their accretion, shown

by their elemental distributions, which are closest to those of the sun. The

fact that no single hypothesis about the origin of meteorites can satisfactorily

explain the peculiarities of the carbonaceous chondrites - especially the petro-

logy of the Type I stones - is known (12), but not much discussed. As asteroid -

sized bodies could not hold an atmosphère and liquid water for any appréciable

time, the argument goes, and since they are so far from the sun that their free

energy is slight, conditions which would hâve permitted the development of life

on asteroids were well-nigh impossible. Of course, the synthesis of the impro-

bably high quantities of organic matter in carbonaceous meteorites is also

unlikely under the presumed conditions. As SAGAN has written: «About

10‘2% of ail meteoritic material which has fallen on the Earth is organic matter.

For comparison, the mass of the Earth is 6 x 10 ^ gm; the mass of the biosphère

- ail the living and non-living organic matter on Earth - is a few times 10 l 'gm.

Thus, the Earth is composed of something like 10'^% organic matter, and most

of this is of biological origin. Why is there a million times more organic matter

in the asteroid belt than on the Earth?» (13, p. 335).

An alternative concept - frequently debated and equally frequently rejected -

is the hypothesis that the asteroids are the remaining débris of a once-existing

planet which exploded as the resuit of some unknown cause. The first serious

considération of this problem in recent years is represented by the work of

OVENDEN (14), who has shown that discrepancies between the orbital eccen-

tricities of the planets in our system and the masses of the presumed perturbing

bodies could best be resolved by assuming the prior existence of a massive

planet between Mars and Jupiter. The means by which such a large body could

be disrupted are unknown. OVENDEN wrote : «Two major problems remain.

First, what physical process caused the sudden dissipation of A (the huge mass

which should be in the présent asteroidal belt)? From the point of view of

the dynamical arguments presented here, it is porbably true that A was always

in the form of a ring. But while it may be difficult to «explode» a planet, it

would seem even more difficult to dissipate a ring suddenly after it has been

quiescent for 4.5 x 10^ yr. Second, only ~ 0.1 M©/Earth mass/ seems now to

résidé in the asteroid belt. What has happened to the other 89.9 M©?» (14).

200

G. CLAUS

A confirmation of this work was supplied in 1976 by Van FLANDERN,

who showed that backwards intégration of the previous perihelion passages of

60 well-observed comets of long period demonstrates that most of these inter-

sect at nearly the same point. He concluded : «Taken in conjunction with the

already-existing evidence, these new results leave little room to doubt that a

Saturn-sized planet did exist between Mars and Jupiter 16 million years ago,

and then violently exploded». (15).

It is, of course, beyond my compétence to judge the correctness of these

fïndings. It may be remarked, however, that were it true that a planet of 90

times Earth mass existed in the présent asteroidal belt 16 million years ago,

then life could indeed hâve developed at such a distance from the sun, and it

would be feasible that its remains should reach the Earth embedded in the

carbonaceous meteorites. En passant, it was recently emphasized that carbona-

ceous chondrites hâve approximate cosmic exposure âges of 15 million years

(16).

The identity of the organized éléments

In our original report, we gave the name «organized éléments» to the micro¬

structures observed in the investigated meteorites, and for the sake of simplicity

and purposes of identification, we described five types, or broad morphological

categories. As alternatives to our interprétations, others offered variations or

combinations of four explanations relating to the nature and origin of the

organized éléments.

1) In the initial stages of the debate, the main argument of the critics was

that the organized éléments were terrestrial contaminants - at least ail but

the smallest and simplest, relatively featureless spheroids, which were said to

be minerai grains (17-19). The most frequently voiced view was that those or¬

ganized éléments which exhibited complex morphologies were spores or pollen

grains originating either in the laboratory, or having entered the stones at the

place of fall or during muséum storage.

2) A second interprétation - especially favored later in the debate - was

that practically ail of the organized éléments were actually minerai grains,

which we had simply mistaken for fossils on account of their «biological ap-

pearance». Among the analytical techniques applied to individual organized

éléments, or such which were embedded in the minerais of the stones, was

an électron microprobe study undertaken by myself and colleagues (20). The

results unquestionably demonstrated that the forms in question had minerai

compositions which corresponded to those of the meteorite, and that they

were indigenous to the stones. After publication, these findings were interpreted

as admissions on our part that the organized éléments are simple minerai grains

(19, 21). Furthermore, those objects which has been demineralized in order

to demonstrate their organic matrix were claimed to represent the unorganized

organic matter of the meteorite (22). Thus, either minerai grains became en-

dowed with complex morphologies (23), or objects clearly containing organic

MICROSTRUCTURES IN METEORITES

201

matter, which had had sufficiently complex morphologies to be earlier seen

as probable terrestrial contaminants (19, 21), suddenly became featureless.

This chemical probe of selected, individual organized éléments showed that

they were indeed mineralized (in our view, fossilized) objects. The resuit was

that their indigenous nature was then acknowledged, but their biogenicity

denied. Such reinterpretation seems to rest on circuitous logic and to ignore

completely the fact that three-dimensionally preserved fossilia (as distinct

from imprints) are, in most cases, permineralized.

It is also of a certain historical interest that a single object, the «type 5

organized element,» was definitely identified by different critics as an indige¬

nous minerai grain (a rare pseudomorph of troilite) by MUELLER (23) and

as an altered terrestrial contaminant (a ragweed pollen grain) by FITCH and

ANDERS (24). This disagreement among our opponents was authoritatively

settled in 1966 by BOSTROEM and FREDRIKSSON (25) in favor of Mueller’s

view. These authors rejected Fitch and Anders’ pollen grain identification,

since it had been based «entirely on morphological argument». That Mueller’s

claim about the disputed form being a troilite particle had also been based

exclusively on morphological interprétation was not mentioned by the later

authors.

3) Still other critics recognized that some of the organized éléments migut

indeed be indigenous, and might consist at least partially of organic matter.

MORRISON, for instance, who was impressed by the varied crystalline growth

patterns of ice snowflakes, hypothesized that the meteoritic organic matter may

similarly show elaborate structures, without being biogenic (26). In a sériés

of papers from the Soviet (22, 27-29), organic matter in the stones was des-

cribed to be présent in three forms: a) dispersed, oily bituminous matter; b)

small conglomérations around minute minerai condensation nuclei; and c)

coatings around larger minerai grains. Ail of these inclusions were obviously

abiogenic.

4) It was perhaps only to be expected that investigators involved in experi¬

mental synthesis of prebiotic organic forms thought that the organized éléments

were, in effect, indigenous masses of organized but non-biogenic objects, resem-

bling their own laboratory products. Thus FOX proposed that at least the sim-

pler forms were similar to his proteinoids (30, 31), and PERTI (32) suggested

that the Jeevanu or «particles of life» synthesized by BAHADUR, PERTI

and others of their group (33, 34) had remarkable resemblances with the orga¬

nized éléments found in meteorites.

5) At a rather late stage in the debate, two papers appeared by ORCEL and

ALPERN (35, 36), which actually denied the very existence of structured

aggregates of indigenous organic matter in the stones. In their first publication,

the authors dismissed our findings as obvious contaminants and proceeded to

show in thin section and ultrathin section studies that the inclusion bodies

they saw were ail minerais. Their second paper was a microprobe analysis of the

distribution of organic carbon in the Orgueil and the Cold Bokkeveld stones.

They found «... une dispersion assez régulière du carbone dans le ciment

202

G. CLAUS

silicate. . .» (36). However, they admitted that, because of the limitations of

their technique, they could not State that this dispersion is absolutely homo-

genous, i. e., that, there is only amorphous carbon présent.

One interesting example of how these various reinterpretations were combi-

ned - sometimes on the basis of distortious of our own fïndings - is represented

in a 1964 publication of VDOVYKIN (22). Following his own description of

certain minerai phases in the Orgueil meteorite, which he in part identified

with the organized éléments, he wrote, in connection with our 1963 micro¬

probe study, «... there appeared a paper by NAGY et al. ... which fully

confïrms the conclusions presented above. The authors show by means of

local X-ray analysis that the globular microstructures in the Orgueil and Ivuna

chondrites, morphologically identical with the organized éléments, contain

up to 40% Fe, 6% Mg, 10% Si, 20% Ca, 2% Ni, up to 10% S and 3% Cl, are

essentially hydrous ferromagnesian silicates (chlorite - serpentine). Some of the

particles contain no éléments with Z > 11; these are inclusions of carbonaceous

matter.» (22). It is remarkable that the Russian author could so blatantly mis-

read figures presented in a table, where the elemental composition with Z

number above 11 of 21 isolated, untreated organized éléments was presented,

plus that of three untreated objects in thin sections, three demineralized pel-

licles, and a minerai control. No object studied contained more than four of the

above-named éléments, the majority only two: iron and chlorine, or iron and

nickel. One object out of the 28 analyzed showed calcium and sulphur, and

it was pointed out that this was probably a gypsum-containing particle. The

high magnésium and Silicon values mentioned were taken by Vdovykin from

the chlorite minerai which had been used as a control. Vdovykin’s «inclusions

of carbonaceous matter» were, of course, those isolated objects which had been

demineralized by HCl treatment. As though ail of this were not enough, it may

be noted that the author had earlier dismissed the organized éléments as terres-

trial contaminants through an equally blatant misrepresentation of two of our

earlier publications (1, 37), as well as those of STAPLIN (38) and of PALIK

(39). It goes without saying that in ail of these works, Controls were run for

laboratory contaminants and for contaminants présent in the stones. In this

connection, VDOVYKIN wrote: «... the carbonaceous chondrite contains. . .

a certain amount of biogenic contaminations which cannot be completely

removed because of the porous character of carbonaceous chondrites. These

impurities may be spores, pollen grains, and even paper fibers described as

«organized éléments». . .» (22). None of the papers cited ever identified these

items as organized éléments : the authors had simply pointed out that a few

spores, pollen grains and cellulose fibers were occasionnally observed in prépa¬

rations as obvious terrestrial contaminations.

This particular paper was probably unique in combining three explanations

of our fïndings - i. e., that everything which we had considered as an organized

element was a minerai, a terrestrial contaminant, or an aggregation of featureless

organic matter - and in simultaneously misrepresenting our work by incorrectly

inferring that we ourselves had proven these points in our own studies. But

MICROSTRUCTURES IN METEORITES

203

while this publication represents an extreme case, it was not entirely atypical

for the period.

By the 1970s, the situation respecting organic inclusion bodies in carbona-

ceous chondrites had changed considerably. The assertion that the stones had

undergone large-scale contamination by terrestrial organisms during their post-

fall historiés was no longer a primary claim, since in the intervening years the

results of extensive studies had shown that the number and weight of conta-

minating structures and/or microorganisms were unexpectedly low (40-43).

Furthermore, the idea that our simpler forms (organized éléments of types 1

and 2, which constituted the bulk of the numerical counts) were obvious minerai

grains, was thrown into doubt by two studies (44, 45) appearing in 1973 and

1971, respectively. The first of these was a fluorescence investigation of embed-

ded fragments of the Orgueil meteorite, in which the authors demonstrated

that organic aggregates of 2/im size are présent in massive numbers in the

amorphous matrix of the stone. The researchers also published transmission

électron micrographs of submicronsize particles which they took to correspond

to the fluorescing material. In the second paper (45), a palynological study

of the Orgueil stone, the presence of large numbers of indigenous, organised,

organic particles in the 2 to 50/im range, with a majority about 9/im in size,

was demonstrated. This latter paper will be treated in some detail later.

In the context of these renewed assertions that indigenous, organized, organic

particles are indeed présent in Type I carbonaceous chondrites, the results of

transmission and scanning électron microscopie investigations of the Orgueil

meteorite are presented below.

MATERIALS AND METHODS

The Orgueil meteorite sample originated from the collection of the Montau-

ban Muséum in France, and was obtained through the courtesy of Dr. A. Cavaillé.

It represented originally a complété stone with fused crust weighing ~ 80g,

from which a 49.27 g piece was brocken off. This rock has been kept since

1962, wrapped in aluminium foil in a hermetically-sealed glass jar. Several

prior experiments hâve been conducted on specimens from this stone (20, 41,

45,46, 47). Fragments were separated from the breakage surface with stérile

instruments, and a selected piece was placed between aluminium foils and pres-

sured by the thumb. Particles from the fragment thus crushed, in the size range

of 1 or 2 mm or smaller, were picked out with a stérile forceps for the investi¬

gations.

For the transmission électron microscopie (TEM) studies, the meteorite

grains were impregnate with and embedded into Spurr low-viscosity medium

(Polysciences, Inc., Warrington, Pennsylvania), using the standard formulation

(48). Infiltration was carried out for 24 hr under continuous agitation on a

rotary shaker, while oven-dry gelatin capsules served as casts for embedding. Curing

204

G.CLAUS

took place at 70 C for 24 hr. No déhydration or staining of the specimen

was undertaken. Silver sections were eut on a Porter-Blum MT 2 ultramicrotome

using a 3 mm edge Dupont diamond knife. The ribbons were mounted on 300

mesh Formvar coated grids, and were viewed in a Phillips 200 électron micro¬

scope at 60 KV. Pictures were printed on Kodak polycontrast paper.

Two types of préparations were made for the scanning électron microscopie

(SEM) investigations: intact meteorite grains were mounted on the usual alumi¬

nium dises, gold coated to ~ 300 Â thickness, and viewed in a Cambridge

«Stereoscan» microscope, at 20 KV, equipped with an energy dispersive X-ray

analyzer (EDAX International) operated from 9 to 50 KeV, with a resolving

power of 800 Â ^ and elemental détection capability of 10"^ g above Z > 5; ail

éléments présent appearing in a simultaneous display. This instrument has a

built-in computer which automatically strips the display from noise, high back-

ground levels, and overlapping secondary peaks, and détermines peak heights

in relation to an internai standard (49). Elemental analyses were performed

on each selected object and on its surroundong area.

In the second type of préparation, the sample holder dise was covered with

a stérile polyethylene sheath, upon which were placed the meteorite fragments.

The préparation was then etched with 48% HF. After drying under cover (about

24 hr), the samples were gold coated and investigated as described above. This

treatment permitted the in situ visualization of HF résistant organic remains.

No washing of these préparations was attempted; nor was the HF treatment

followed up with HCl extraction to remove the rest of the inorganic material.

A pièce of the Gunflint chert served as a positive control in these experi-

ments. It was obtained with the coopération of Dr. A. A. Ekdale, and came from

the collection of the Department of Geological and Geophysical Sciences,

University of Utah, Sait Lake City. It originated from the Biwabik Banded Iron

(Minnesota) portion of this formation, showing the typical stromatolitic struc¬

ture. This particular shale has been dated at 1.8 eons. Pétrographie thin sections,

kindly prepared by Prof. Dr. A. Papp, Micropaleontological Institute, University

of Vienna, Austria, exhibited the typical Gunflint flora of filaments and uni-

cells (50, 51). The chert was treated identically to the meteorite samples, with

the exception that no TEM studies hâve been performed on it.

During ail sample préparations, extreme measures at cleanliness, as usual

with meteoritic studies, were adhered to, the details of which hâve been reported

several times elsewhere (2, 37, 46, 47).

RESULTS

Transmission électron microscopie studies

The results of the transmission électron microscopie studies were in agree-

ment with earlier flndings. The minerais within the matrix (by which is meant

MICROSTRUCTURES IN METEORITES

205

the inorganic or organic amorphous or slightly crystalline matter) exhibited

a great variety of forms. Lathe-like filaments, as described earlier on the EM

level (12, 52-54), embedded in the common non-crystalline matrix (see at A),

are illustrated in fig. 1. Flaky, layer-lattice silicates hâve been found, a specimen

of which is shown in fig. 2. It is similar to those depicted by previous workers

(53-56). On fig. 3, a portion of the meteorite matrix with fewer crystalline

structures can be seen, although the curved edges of the typical silicate minerais

are plainly visible in the lower middle portion of the picture (area C). Rhom-

boidal crystals occur on both sides (underneath A), while clearly amorphous

material is présent in the lower left corner (B). What might be magnetite glo¬

bules (highly electron-dense, more or less spherical structures exhibiting some

hexagonal faceting) occupy the upper right corner (D). In the center of the

figure is a micro structure with an electron-transparent interior, delimited from

the surrounding material with what seems to be a double wall, at least on its

right side. It has the following dimensions: length, 0.51/im; width, 0.36/im.

The pseudohexagonal shape of this form should not be confused with those

structures first described from the light microscope and named by STAPLIN

as Caelestites sexangularis (38), and in subséquent studies designated as «box-

like objects» (57-59). (Findings relating to such objects will be discussed in

another publication). The présent form and most of those on the next plate

seem to be similar to the organized organic matter found in ultrathin sections

of unextracted meteorite stones by Van LANDINGHAM et al. (60), and later

by ALPERN and BENKHEIRI (44). The majority of these objects hâve appa-

rently one or two less electron-dense areas in their centers. It should be pointed

out that such transparent areas could hardly represent a minerai grain, around

which the organic matter would hâve condensed (as presumed by the French

authors (44)), since such a crystal would hâve shown up in the thin sections.

No materials which could hâve served as condensation nuclei are évident in

the published micrographs.

At low magnification, ail the individual bodies on Plate 2 with the exception

of fig. 13 could be identified with one or another of the forms in the published

micrographs of these two teams of authors. At higher magnifications, however,

details emerge which hâve not been described by the previous investigators.

In fig. 4, 6, 7, 8, and 9, structures of the same object are presented at three

magnifications. The body might hâve had either a spherical or an elliptical

form, eut somewhat tangentially, with a long axis of 0.56/im and a short axis

of 0.46/im. Fig. 4 shows that the structure is completely embedded in the

undisturbed minerai matrix, which exhibits relatively poor crystallinity at this

place. Comparing the pores in the matrix with the size of the object, it is ob-

vious from this and other micrographs that the pore size of the Orgueil meteo¬

rite is typically much below the l/im diameter; thus it is impossible that even

these relatively small structures should hâve become lodged in the stone as a

resuit of contamination.

In fig. 6, the object is shown at higher magnification, permitting the obser¬

vation of the spines on the external surface of its wall (left side); the layered

206

G. CLAUS

wall, best visible on its right; the attachment of the stalk; and the peculiar,

centrally-located vesicular System. The average height of the spines is 30nm,

and some show either a canal with an internai diameter of 3 nm, or at least a

pore in their tips (see arrows in fig. 7). Apparently the spines cover the whole

surface, with the exception of the area where the stalk is attached. The wall

is double layered (fig. 8), with great similarities to the structure of gram négative

microorganisms, especially that of Cyanophyta ; therefore, the désignations of

YOST (61) will be used. L4 + L3 (Pl) = 11 nm; L2 + L1 = 4nm; Cm = 3nm.

Thus, the total wall thickness is 18nm, approximately one-half that of a typical

blue-green algal cell wall (62). One has to point out, however, that no terrestrial

bacterium or blue-green alga is known which would hâve such a spinous cell

envelope.

The attachment of the stalk to the object is shown enlarged in fig. 7. It is

évident that the stalk is a cylindrical structure, with a broadening collar at the

place of attachment to the body. The diameter of the stalk itself is 140 nm;

while at the top of the neck it is 180nm wide. It pénétrâtes through the wall

of the body to a depth of 35 nm. Its total length cannot be established, but its

visible length is 0.56/im.

In the center of the body a peculiar structure, composed of at least six

vesicles, is visible (fig. 9). The largest measurement of the total complex is

0.2/im, and the length of the elliptical upper vesicle, which is the best preserved,

is 80nm. At least three of the vesicles hâve spots of electron-dense material

within their centers, and they also possess their own limiting membrane, measu-

ring, where visible, 3nm. Microtubule-like branching canals seem to pass from

the vesicles to the surroundings (fig. 9, arrows).

Fig. 5 is taken with the same magnification as fig. 4, but from a different

préparation. It represents basically the same kind of object, except that it is

apparently a mirror image, with the remnants of the stalk (at arrow) attached

on the lower right corner. The diameter of the body is 0.5/im; the height of the

well-visible spine in the upper left corner is 48nm. Where the wall can be seen,

its structure and dimensions are the same as those of the previous object. The

visible portion of the stalk has a diameter of 74 nm, with a width at the collar

of 102 nm, and a length of 48 nm.

Fig. 10 represents an object resembling a terrestrial yeast undergoing budging.

Its total length is 0.46/im, that of the main body 0.3/im, and of the bud 0.16/im.

The width of the main body is 0.18/im, and of the bud 0.14/im. The wall is

similar in structure to those of the previously-described objects, but it is clearly

visible only on the lower side of the main body; at other places it is partially

or completely covered with some extraneous material. Within the main body

there are two, more electron-dense profiles, one circular (above and to the

right of A) and the other elliptical (above and to the right of B): The circular

feature has a diameter of 42nm. The elliptical structure, at high magnification,

is seen to be composed of two vesicles, each with an internai electron-dense

spot. They closely resemble those of the object in fig. 9. The length of the better

preserved one is 74 nm.

MICROSTRUCTURES IN METEORITES

207

A fine, reticular, fibrillar network is discernible in the central portion of

what appears to be the bud, mimicking DNA strands. The width of these fibrils,

which are of two types, is 1.5 and 2 nm, respectively (about the same as blue-

green algal DNA (63)).

The object in fig. 12 is, in general, similar to those in fig. 5 and 11, except

that it has several small protrusions on its surface. Fig. 13 shows what is most

probably an euhedral magnetite crystal. It is the same approximate size range

as the two bodies in fig. 11 and 12, having a diameter of 0.23Mm. The electron-

opaque nature of this minerai clearly distinguishes it from the organic material.

Fig. 14 to 16 depict the cross section of an object with an exceedingly

thick internai wall layer. The external layer (L4 + L3), best seen at arrow,

has approximately the same thickness as in the form in fig. 4, i. e., 11 nm.

However, L2 + L1 varies from 54 to 88 nm with an average of 66 nm. Cm =

6 nm; the average total wall thickness is 80nm. (It should be noted that the

thin electron-light layer surrounding the whole object is not part of the wall,

a fact which can be ascertained from its continuation around the sickle-shaped

white area above the body). The length of thé object is 0.66/nm; its width,

0.54/im. On its lower left side, the body shows a neck with a base of 240nm

and a height of 88 nm, resulting in a total wall thickness of I68nm in this area.

A feature within the wall is suggestive of the presence of at least one canal

traversing it, connecting the inside of the body with the exterior. This is mani-

fested within the neck on the lower left side (above A), where the électron

lucidity of the area, compared with the rest of the wall, is indicative of the

presence of a channel just below the plane of sectioning. The interior of the

entire form is filled with unidentifiable débris. The structure of the left of the

neck (between arrows) does not belong to the body, but is part of the surroun¬

ding matrix.

Fig. 15 is an over-illumined view of the body and its surrounding at the

place of junction between the external object and the neck (arrows). It is clear

from this picture that the object is merely appressed to the body.

The light, sickle-shaped area above the form was apparently an empty space

prior to imprégnation with the resin. However, the slight opacities in it indicate

that it was penetrated by the embedding medium. Thus, the body was not

torn from its matrix during sectioning, but was moved from its original position

before processing. Fig. 16 shows that the object indeed fits the space from

which it was displaced, proving that originally it was intimately embedded in

the matrix, but was turned by approximately 180 (note location of neck

canal at A). During displacement, an electron-dense granule apparently became

pressed into the wall (see at B).

As a whole, this object is closely reminiscent of a terminal heterocyst of a

Nostocacean Cyanophyte, such as a member of the Rivulariaceae. However,

it also resembles a cross section of the abundant marine fossil of unknown

affinities, Tasmanites sommeri Winslow.

208

G.CLAUS

Scanning électron microscopy

Some of the fïndings of the SEM investigations are illustrated in Plates 4, 5,

and 6. Plate 4 depicts objects which are, for the most part, familiar from the

literature. Fig. 17 and 18 compare two spherical bodies of approximately

equal diameter (6.8 and 6.2/im, respectively), one (fig. 17) after HF treatment,

the other from native préparation. The irregularities on the surface of the first

body seem to be the resuit of déposition of materials after the évaporation of

the acid, and should not be mistaken for layering. Some surface layering can,

however, be discerned in the structure shown in fig. 18 - a feature found also in

the SEM picture of one of the acid-treated «hollow spheres» from the Orgueil

meteorite of ROSSIGNOL-STRICK and BARGHOORN (45) (Plate 3, fig. 2).

The indigenous, organic nature of objects of this type has been established

by these investigators, and is now confirmed : they contain carbon, in addition

to iron, but hardly any Silicon. Whether they are prebiological or biogenic is

still an open question.

In Fig. 19, a discoidal body with notable surface structure is shown. lts dia¬

meter is 5.6/im; height, 2.6/im. Several similar structures hâve been illustrated

by JEDWAB, both from pétrographie thin sections (64) and from density-

gradient separated material viewed by means of SEM (65). This author interpre-

ted such forms as one of several extraterrestrial types of magnetite. In fig. 20 the

EDAX spectrum of this object is presented, taken at 10 KeV. The body unques-

tionably contains considérable quantifies of iron, but the relative amounts

of aluminium, silver, potassium and sulphur make it an interesting species of

magnetite from the point of view of composition as well as that of morphology.

The well-delineated objects in Fig. 21 (measuring approximately 4/im in

length) are basically composed of iron, with some traces of copper. (These

were the only structures found in the whole investigation which showed the

presence of copper). Since oxygen could not be determined, it is impossible

to décidé whether these particles represent magnetite or limonite. However, the

peculiar feature of radiating spokes (underneath A) in the object at the left of

the figure is quite reminiscent of similar details described several times from

pétrographie sections in the light microscope and held to be characteristic for

meteoric magnetite (12, 25, 35, 64, 65).

Another supposed extraterrestrial form of magnetite, as described by JED¬

WAB (65, 67), is shown in Fig. 22. Here are seen submicron-size particles, iden-

tical to each other in dimensions, forming an aggregate of irregular shape.

According to JEDWAB, such «magnetite aggregates» usually develop in cavities

where they cover the concave walls. The picture shows that these particles

occupy a highly convex surface, and they continue on the right side, below

the area visible in this micrograph. The individual particles hâve diameters of

0.1/im, are connected with each other by some kind of fibrillar material, usually

hâve a prominent spot on their surface, and sometimes are enveloped jointly

in a more or less transparent mass (see under A), which is much more easily

recognized at lower magniFication. Some apparent faceting is observable, inter-

preted in similar aggregates by KERRIDGE (66) and by NAGY (12) as repre-

MICROSTRUCTURES IN METEORITES

209

senting possible crystal faces of magnetite. On account of their small size, KER-

R1DGE could not define the elemental composition of the individual grains

by microprobe; but since Ke observed occasional concavities in their surfaces,

he pointed out that such structures occur in terrestrial spinels. It should be

noted, on the other hand, that the faceting on the surface of these particles

is not necessarily indicative of crystalline nature, since it could equally well

be the resuit of compression.

According to our studies, these objects are definitely not magnetite, as we

were able to take elemental spectra from individual granules. The composition

of these forms (averaged from five déterminations), expressed relative to Fe as

unity, is as follows : Fe^ .00 S ip.74 A k).24 M g0.22 Ca 0.22 A g0.11 Mn 0.08 Ni 0.07

CIq o 8 c O 26 S trace- Tlie composition of the particles would seem also to rule

out a number of other possible minerai identities.

In fig. 23, on the other hand, may be seen individual granules of similar

size (from 0.2 to 1.2/im), scattered in the matrix among other minerai grains,

which seem from their elemental composition to be indeed magnetite particles.

Fig. 24 and 25 on Plate 5 depict some highly siliceous objects embedded

in silica matrices * the First from an untreated Orgueil meteorite specimen;

the second from an untreated fragment of the Gunflint chert. The texture and

cleavage patterns of the matrices are remarkably similar, as are also their elemen¬

tal compositions. This type of almost pure silicate matrix, which does occur

in Orgueil and is suggestive of the chalcedony of the chert, contrasts sharply

with the apparently layer-lattice silicate matrices shown in fig. 18 and 23.

A third and again fundamentally different type of matrix in Orgueil may

be discerned in fig. 26 and 27. In the former, a spinous object is also Visible,

apparently torn out from its matrix, as evidenced by the hole beneath it, in

which are retained some of the spines (at B). This spheroid has a diameter of

2.4/im, and the length of the spines varies from 0.3 to 0.6/im, with an average

diameter of 0.1/im (68). Its immédiate surrounding does not show much surface

structure, but lower magnification (fig. 27) reveals that the body is lying on top

of a meteorite fragment. The darkness of this figure is the resuit of the deep

location of the entire structure, which is well below the uppermost surface

of the fragment, the latter being indicated by the ridge (at A) in fig. 27. B

désignâtes the area in the hole from which the EDAX readings were taken,

and C the région of the matrix which was probed. The results obtained for the

elemental compositions of the spinous body, the area of the hole, and that of

the matrix are given in Table I. It is noteworthy that the material making up

the side of the hole is intermediary in composition between that of the body

and the pure matrix. This might resuit from the inclusion of retained spines

in the analysis of the hole. The presence of silver in this matrix is also interes-

ting, since it has not been observed in other matrices investigated, but rather

appeared only in discreet particles. Here also, both the matrix and the object

are carbonaceous.

Fig. 28 shows what appears to be a partially collapsed, fossilized spore

from the Gunflint chert after HF etching. Its diameter is 11/im, and its height

210

G. CLAUS

Table I. — Relative Elemental Composition of Complex in fig. 27.

Matrix

C 0.11

Mg 0.02

Al 0.08

Si 0.18

Cl 0.03

Ca 0.07

Ti -

Cr 0.13

Fe 1.00

Ni 0.13

Ag 0.22

W 0.13

«Hole» Object

0.12 0.17

trace

0.06 0.07

0.21 0.18

0.03 0.02

0.08

0.09 0.09

0.12

0.18 0.20

1.00 1.00

0.12 0.11

0.16 0.13

0.15 0.09

— : not found.

9.6/lm. In a sériés of articles, BOUREAU (69, 70) demonstrated that most

of the spheroidal structures found in Precambrian materials are stages in the

agglomération of bacteria, which eventually become surrounded with solidified

mucilagineous matter to form distinct colonies. However, the structure depicted

in this figure could not represent one of these forms, because even with very

high magnification under the scanning électron microscope (50,000 x) no sur¬

face details other than the fact that the wall is porate and covered with small

spines, about 0.1 /im in height, can be visualized. The body has one visible

dimple on its lower left side, lflm wide and 0.8/lm deep, and a protubérance on

the right side of approximately the same dimensions. The general structure is

very similar to the oosphères occuring in the Vaucheriaceae ; although the

fossil is only about one-sixth the size of that typical for extant members of the

genus Vaucheria. It might, however, also represent a single, extinct tetraspore.

In fig. 29, one can see a dichotomously dividing portion of a filament from

an HF-etched Gunflint fragment. In the foreground there are two parallel main

branches, each measuring 35/im in width. Before bifurcation (at A), the fila¬

ment is 60/lm wide. Two side branches are présent, one in the front (B) and

the other coming from underneath the main filament (C), the first having a

width of 10/xm, the second of 20jUm. The second side branch also bifurcates

(at U), giving rise to two 10/im-wide filaments. Since there is no sign of cross

walls, the entire habit of this structure is reminiscent of the syphonaceous

organization of members of the Xanthophycean Vaucheriaceae family, or that

of the green alga Protosyphon. However, the marked diversity in width exhibited

among the main filament and the primary and secondary branches is a charac-

teristic not found in any of the modem yellow-green or green algae. On the

other hand, this habit is quite characteristic for certain Florideaceae , such as

MICROSTRUCTURES IN METEORITES

211

some Ceramium or, especially, Bostrychium spp. The extant représentatives

of these forms, however, are always multicellular.

Such highly developed plant remains as those depicted in fig. 28 and 29

hâve not yet been reported from the Gunflint formation. As mentioned above,

the affînities of the filament are uncertain; however, its complex structure

and large dimensions seem to attest its possible eukariotic nature (71,72).

Although these samples were etched with HF, their EDAX spectra indicate

that considérable amounts of minerais are still présent. In addition to iron

and other cations, quantifies of Silicon remain in these microfossils. Their

excellent State of préservation is undoubtedly due to their thorough permine-

ralization. The results of the elemental analyses are given in Table 2, together

with those for the filament complex of fig. 34, Plate 6.

Table 2. - Relative Elemental Composition of Objects Depicted in fig. 28, 29, 34 and 35.

Crystal

34 Main

Filament

Matrix

34 Narrow

Filament

0.17

0.19

0.21

0.35

trace

0.02

0.03

trace

0.02

0.04

0.08

0.14*

0.12*

0.30*

0.17*

0.25

0.16

0.30

0.20

0.16

0.12

0.06

0.22

0.14

0.02

0.06

—

0.11

0.03

0.09

0.16

0.06

0.12

0.07

0.11

0.12

0.09

0.06

0.11

0.04

—

0.19

1.00

0.05

1.16

0.18

0.07

0.14

0.06

0.08

- : not found; *:The high values may resuit in part from the fact that during storage

the stone was wrapped in aluminium foil.

On Plate 6 are depicted only filamentous structures, some clearly minerais,

others of debatable nature and origin.

The hollow filament shown in fig. 30 is from an HF-treated sample of the

Orgueil stone. Its width is 1.2(tm, with a total wall thickness of 40nm (68).

Note that the double lines visible on the sides of the filament do not represent

double layering, but are rather an optical phenomenon, resulting from the

translucency of the object. The EDAX spectrum of this structure, when expres-

sed in terms of Fe as unity, is as follows : *-- 1 .2^0.1 :2 e 1 .fO'l ,(O0.0^80.4■

Source : MNHN, Paris

212

G. CLAUS

The proportional expression of éléments is somewhat misleading here, since

the major éléments (iron, Silicon, aluminium) ail gave very low absolute readings.

Such was also the case with several other objects (to be illustrated elsewhere)

which were apparently quite thoroughly demineralized by HF etching. The

fact, however, that the major éléments were found, together with carbon, in

about equal proportions, indicates that this structure is indigenous to the météo¬

rite.

The next figure (31) shows a fïlamentous form with a diameter of only

0.6Mm from an untreated Orgueil fragment. It is so intimately embedded in its

surrounding matrix that it serves as a bridge across a fissure. This form is remi-

niscent of that shown by KERRIDGE (52, 53) and tentatively designated as

sepiolite, an identification questioned by NAGY (12, 55). From the EDAX

analysis of the object, it would seem to be mineralized organic matter, and in

any case, is certainly not sepiolite, having the composition : Cq 2 Sq 09 Fe l 0

Si 0.09 Al 0.22 Ni 0.04-

Fig. 32 and 33 each depict rounded (A) and prismatic (B) filaments (C

indicates location of matrix analyses), those of fig. 32 from an untreated Orgueil

sample, and those of fig. 33 from untreated chert. The rounded forms hâve

diameters of 0.8/im. Ail five objects contain various proportions of iron and

Silicon (with the latter in dominance) and the matrices are almost completely

silicaceous. None of these filaments contains any carbon, and they show only

trace amounts of magnésium; thus, they do not appear to be sepiolite either.

In fig. 34, a group of two types of filaments can be seen. There are clearly

septated, larger filaments, more visible towards the upper right side of the

picture, on top of which a bundle of narrower filaments is lying. The whole

assemblage is partially covered by finely crystalline matter, which is evidently

the resuit of the recrystallization of the meteorite’s matrix after HF treatment.

The large filaments are 18 to 20/im wide, with a narrow sheath on the one to

the left, enclosing a trichome of 16/im width, constricted at the cross walls;

the cells are barrel-shaped, shorter than wide, 5 to 10/im long, with end cells

pointed. The exact shape of the end cells is not discernible because of over-

laying material, but from the portions which are not covered, a pointed conical

form can be deduced (see at A). The total length of the assemblage, which

presumably corresponds to the length of the large filaments, is approximately

550/im. With the exception of one or possibly two filaments (to the right of

B), the other large filaments are collapsed. Whereas the left one is simply collap-

sed to a form a U-shape or a longitudinal burrow, the one on the right (to the

left of C) is completely compressed, its end representing the probable remnants

of a cross wall„ the presence of which is signified by the line of submicrosco-

pic pores (visible only at high magnifïcation, but here indicated by arrow) at

the place of their junction. The sheath of the filament to the left is frayed

at its end, and throughout its length shows a flaky, fragile structure. The fila¬

ments to the right apparently hâve no sheaths. The whole structure seems to

hâve been heavily mineralized, as several breakage marks are présent (for ins¬

tance, to the left of D), suggestive of rigidity.

MICROSTRUCTURES IN METEORITES

213

Two structures not belonging to the filaments hâve to be mentioned : at E

is seen a bipyramidal prism in the lumen of a large filament (shown also in fig.

35 at higher magnification), predominantly made up of nearly equal amounts

of iron and nickel (cf., Table 2). At F a pseudohexagonal object is visible,

which is identical to Caelestites sexanguhtus Staplin (38), or the «box-like»

bodies of other investigators - forms very commonly found in Type I carbona-

ceous chondrites. As mentioned earlier, the description of these bodies from

both TEM and SEM findings will be the basis of another paper.

The bundle of small filaments is composed of basically 1.5 nm wide indivi-

dual trichomes without regularly visible septae, the presence of which, however,

is occasionally indicated (see to the left of G). The length of these filaments

is up to 200/im; their ends are obtusely conic.

If terrestrial, both the larger and the smaller filaments would belong to

the Oscillatoriaceae family, the broader ones representing the genus Lyngbya

and the small ones Microcoleus. The unsheathed nature of the filaments to

the right (at B) might suggest a primary State, and in that case one would be

dealing with an Oscillatoria ; on the other hand, if these represent only hormo-

gonia, then they may, indeed, be Lyngbyae.

The facts that the top surface of the meteoritic matrix is visible around

the bottom portion of the picture (H), on which the filaments are apparently

lying, further that they are ail covered with recrystallized minerais, are associa-

ted with a body known from this type of meteorite ( Caelestites ) and with an

iron-nickel minerai (E), would ail support the view that these structures are

not terrestrial contaminants, but are indigenous to the stone. Their fragility

and their individual EDAX spectra (Table 2) confirm that they are minpralized

with éléments présent in the meteorite. The différences in elemental abundances

among the matrix, the large filaments and the small filaments argue against

the possibility that they became imbibed with these éléments as a resuit of the

HF treatment.

Forms corresponding to the major filaments were identified and described

at the light microscopie level by PALIK (39, 43) and Van LANDINGHAM

(42), from the Orgueil meteorite. The small filament was first recognized by

PALIK (39) and photographed and shown by N AG Y et al. (20), also from

Orgueil.

DISCUSSION

The fine morphology of meteoritic structures

In the whole of the literature, there is only one work which is devoted

specifically to the ultrastructural analysis of organic matter in intact carbona-

ceous chondrites with transmission électron microscopy on direct thin sections

(60). There is a second paper containing several TEM micrographs (44), and four

other publications showing at least one picture from untreated meteoritic sec¬

tions.

Source : MNHN, Paris

214

G. CLAUS

The first micrograph seems to hâve been published by MANTEN in 1966

(71), the specimen having been prepared by the LKB laboratories of Stock¬

holm. MANTEN does not give a description of the object, which is a small

(0.3/im diameter) spheroid with an electron-translucent, homogenous internai

area, showing an electron-light center. It is partially delimited from its surroun-

ding by what might be called a wall. It is torn from its matrix, and the wall

is missing on the detached side. This picture was republished by NAGY in 1974

(12). Also shown in NAGY’s book are four micrographs prepared by ALGY

PERSSON in 1963, depicting peculiar configurations in the matrix suggestive of

preferred orientation. In 1966, NAGY published a paper (72) in which the

micrograph of a tripartite object composed of three spheres was incorporated.

An external layer, which might hâve been considered to be a wall, was présent.

The general structure of this form is highly reminiscent of some inclusions

found in high température minerais and identified as such by NAGY himself,

on the light microscopie level, from Precambrian basalts (73). It is probably

for this reason that the early picture of the object no longer appears in the

1974 treatise (12).

Also in 1966, two électron micrographs appeared in the mineralogical study

of ORCEL and ALPERN (35). One of them clearly represents small magnetite

grains, whereas the authors could only speculate about the identity of the

object on the second, which was too small to microprobe (0.3/im). In the text,

they State that the body looks like a microorganism with an internai structure;

however, they présumé that it must be an divine microchondrule, and the

micrograph is already so captioned.

In 1973, ALPERN, together with BENKHEIRI (44), decided to publish

several additional pictures obtained in 1966, but not included in his work

with ORCEL of that date. In these micrographs, which contain electron-trans¬

lucent particles assumed to be identical with the investigators’ fluorescing

particulate organic matter, it is interesting to note the presence of developed,

double-layered walls, especially well preserved in the objects of their fig. 8 and

9. These are not, however, mentioned in the text. Measuring from the printed

photographs, the walls hâve a thickness of ~ 14 nm. A wealth of other details

are also visible in the several forms of their EM figures; it is not, however, our

task to discuss them here, since they were not described by the authors.

The difficulties of preparing ultrathin sections of intact meteorites hâve

led to several alternate methods of TEM studies, such as investigation of pow-

dered samples, acid treated residues without sectioning, sectioned organic

residues, and replicas. Since these are not of direct concern in this paper, only

TAN and Van LANDINGHAM’s work on exhaustively extracted organic residues

from the Orgueil meteorite will be mentioned (74). Direct investigations on a

Formvar grid of these air-dried materials revealed a number of objects, mostly

in the < l/im size range, which resembled the acid-resistant walls of bacteria-

like or other filamentous microstructures. The majority of the longer filamen-

tous forms showed small electron-dense globules, regularly placed in their

interiors. The wall thickness of the objects was estimated as less than 25 nm.

MICROSTRUCTURES IN METEORITES

215

In the ultrathin section investigation by Van LANDINGHAM et al. (60),

ten organic structures are depicted on six électron micrographs. Because of the

low magnification, it is somewhat difficult to evaluate these pictures. However,

the presence of a well-developed limiting wall around most of the objects is

easily discernible. The walls are described as measuring approximately 20 nm.

There are other visible features as well. The wall of the object in flg. 2 can be

resolved to be composed of layers, whereas that of fig. 3 shows a number of

protubérances, in addition to layering. An internai electron-light area is well

visible in the structures of fig. 3, one of which is essentially identical to the

objects of fig. 7 and 8 in (44), or to those of fig. 4, 5, 11, and 12 of this study.

The sizes of the microstructures depicted from TEM works are admittedly

very small: in their majority less than one micron. This is also true for the

présent study. Nevertheless, these objects are not likely to hâve become lodged

in the stone after its entrance into the terrestrial atmosphère, since they are

found thouroughly embedded in matrices where the pore sizes are well under

O.lllm. We had already in 1964 pointed out (75) that our pétrographie studies

indicated a general pore size of less than one micron for the Orgueil meteorite,

and the présent investigations seemed to confirm this statement. The finding

reported above of essentially identical structures in two different specimens of

the meteorite (fig. 4 and 5) further substantiates the claim that the objects

described on the TEM level are autochthonous.

It is pertinent to note that there are known terrestrial microorganisms which

fall in the size range of the meteorite organic forms described from the TEM

studies. These were first found in argillaceous speleo-sediments (76) and later

in soils (77, 78). The recent discovery of this «dwarf flora» of soils, the indi-

viduals of which are barely visible in the light microscope, seems to be of consi¬

dérable significance ; and récognition of their existence was strictly dépendent

on investigations utilizing the électron microscope. (The fact that microorga¬

nisms of comparable size range to the objects described from the meteorite

occur in soil should not, on the other hand, be taken as an indication that the

meteoritic microstructures might resuit from contamination by these forms,

since the morphologies of the latter are decidedly different on the ultrastructural

level. Further, as just pointed out, the pore size of the stone is even smaller

than the measurements of these organisms).

Respecting the use of TEM technique on ultrathin sections of intact météo¬

rites, N AG Y has written that such a project is «difficult and time consuming»,

and that the «... results of these examinations do not lead to much more

definite conclusions regarding the origin of the organized éléments than the

examination in the light microscope» (12, p. 627-628). I can agréé that such

studies are time consuming, for it takes approximately eight solid hours of

microscope time just to find one appropriately sectioned object. Thus it is

not too surprising that KERRIDGE, for instance, failed to see any of the «noto-

rious microfossils» in his EM investigations (53), particularly as he is a minera-

logist who was looking for minerais. He might, however, hâve spared the péjora¬

tive adjective. As BACON wrote: «They are ill discoverers that think there

is no land, when they can see nothing but sea».

216

G. CLAUS

I would question, on the other hand, whether such investigations are no more

conclusive than light microscopie studies. It is possible to demonstrate with

the aid of TEM studies that indigenous, highly structured organic bodies are

présent in the Orgueil meteorite, well embedded in the matrix. In view of the

complexity of their fine morphologies, not much room is left for argument

about their biological or abiogenic origin.

Bodies in the size range reported above were also encountered in the SEM

investigations, and their partially organic nature was ascertained through the

démonstration of their carbon contents by EDAX. They are not depicted in the

présent study, however, because the simplicity of their surface morphology

relative to the other objects scanned did not seem to warrant their inclusion.

Surface morphology of meteoritic inclusions.

As is the case with TEM investigations, studies of Type I carbonaceous

chondrites involving SEM techniques are very few in number. Nine publications

were found in which SEM pictures of meteoritic components appear, but in

most of these the micrographs serve mainly an illustrative, ancillary rôle, rather

than representing results from which conclusions are drawn.

In three consecutive publications, NAGY (79, 80, 12) has provided SEM

images of four objects (alternately, ovoids and one spherical form, only ovoids,

etc.), photographed by DREW in 1968 from the «freshly broken surfaces of

the Orgueil meteorite, «implying that no treatment was employed before the

fragments were scanned. (These would then be the only pictures of «native»

organized éléments prior to those presented in this paper, since in other in¬

vestigations dealing with presumed organic objects, the residue from acid-treated

samples was photographed). The bodies were described as possibly hollow,

with a relatively thin, elastic, organic wall showing beaded surface sculpturing.

NAGY speculated that they might hâve been produced from collapsed mem¬

branes under the vacuum of the gold coating process. The objects were relati¬

vely large : the ovoids having lengths of ~ 30jUm and widths of ~ 28/im, while

the sphere was 28/im in diameter. These forms hâve not been found again since

1968.

BROOKS and MU1R (59) attempted to compare the structured organic

matter of the Orgueil and Murray meteorites with that of the lower Onver-

wacht strata (Lower Precambrian). Whereas they discovered spheroids in the

Precambrian material, which they likened to SCHOPF’s SEM pictures of some

forms described from the Bitter Springs Formation (Upper Precambrian) (81),

they found only the «hexagonal box-shaped bodies» in the meteorites. This is

surprising in view of the fact that organized éléments are quite abundant in at

least the Type I stones, even after acid treatment, as has been shown earlier

(37) and recently confirmed by ROSSIGNOL-STRICK and BARGHOORN

(45). The precambrian forms of the English authors exhibit, in effect, a striking

similarity to structures found in this study both before and after acid treatment

(cf. fig. 17 and 18).

MICROSTRUCTURES IN METEORITES

217

ROSSIGNOL-STRICK and BARGHOORN (45) show SEM images of three

isolated organic objects (one fragmented), recovered after acid treatment. The

authors interpreted the remarkable surface layering of one of their forms as the

resuit of débris déposition from the organic matrix on the wall. Fig. 18, which

is substantially identical with their Plate 3, fig. 3, but is from an untreated

sample, exhibits the same surface layering, indicating that it is apparently

a characteristic of the body in question rather than a preparatory artifact. If

this is accepted, then the authors’ statement about the absence of any surface

morphology in such structures is thrown into question.

Papers devoted to the mineralogical study of carbonaceous chondrites also

carry occasional SEM pictures. Thus ORCEL et al. (56) depict a gypsum particle

and a flaky layer-lattice minerai (rather similar to the TEM object in fig. 2 of

this study); and KERRIDGE and MACDOUGALL (82) illustrate two isolated

olivine crystalç. The most extensive mineralogical studies, however, are undoub-

tedly those of JEDWAB (65), who utilized SEM for a detailed investigation of

a great number of microstructures separated through a density gradient tech¬

nique from Type I carbonaceous chondrites. The author identified ail of the

depicted objects as representing different types of magnetite. As far as one can

ascertain from the methodology employed, the whole identification proceedure

was based solely on the facts that these forms were not soluble in CCI 4 and had

a density greater than 3.3 (X-ray diffraction measurements and identifications

were carried out on only a few objects in pétrographie thin sections). The

variety of shapes found by this investigator is remarkable; he even created a

spécial systematic order to accomodate them, since most are completely unlike

terres trial magnetite in their form. Among the more notable are disc-like and

spiral stacks of platelets, framboidal structures, individual plates with supposed

corrosion features showing diverse morphologies, aggregates of small spherules,

spherical clusters, etc. Pictures of the «perfect» framboidal structure and one of

the longest spirals yet to be found were produced by LEWIN as décorative illus¬

trations for a recent popular paper on carbonaceous chondrites (83).

It has aire ad y been noted that many of Jedwab’s magnetite specimens,

in both pétrographie thin sections (64) and SEM (65) préparations, show re¬

markable resemblances to biological forms (12). One cannot but agréé with

this observation; and many similarities could be brought to attention. Thus :

JEDWAB (64) fig. 10 with SCHOPF (84) fig. 56a ; JEDWAB (64) fig. 11 with

BOURRELLY (85) Plate 24, fig. 2; JEDWAB (64) fig. 12 with STAPLIN (38)

fig. 6 or with Van LANDINGHAM (42) fig. 7; JEDWAB (64) fig. 24 with

OBERLIES and PRASHNOVSKI ( 86 ) fig. 5; JEDWAB (65) fig. 1 with FISHER

et al. (87) fig. la; JEDWAB (65) fig. 18 with VOZZHENNIKOVA ( 88 ) Plate 1,

fig. 1 or with VENKATACHALA and SHARMA (89) Plate 1, fig. 21; JEDWAB

(65) fig. 31 with BROOKS and SHAW (90) fig. 11, 14b; JEDWAB (65) fig. 43

with LOPUCHIN (91) fig. 3 d; JEDWAB (65) fig. 45 with BROOKS and MUIR

(59) fig. 1 or with KERRIDGE and MACDOUGALL (82) fig. 2; JEDWAB

(65) fig. 48 with ENGEL et al. (73) fig. 2b; JEDWAB (65) fig. 51 with BOUR¬

RELLY (92) Plate 8 , fig. lia; JEDWAB (65) fig. 52 with NAGY (79) fig. 2b

or with ROSSIGNOL-STRICK and BARGHOORN (45) Plate 3, fig. 1 or with

218

G. CLAUS

SCHOPF (81) Plate 1, fig. 4 or with BROOKS et al. (93) fig. la; JEDWAB (65)

fig. 58 with BOURRELLY (85) Plate 40, fig. 9 - an assemblage which consists

of minerais other than magnetite; biological forms both recent and extinct,

some from marine ooze; possibly mineralized, prebiotic organic matter resem-

bling some terrestrial Precambrian microfossils; skeletons of marine microorga-

nisms; and forms occuring in air pollution samples, with particles of terrestrial

origin.

Of course, it would be patently unscientiflc on my part to claim that these

resemblances constitute identifications. Nevertheless, one would like to know

how it is possible that JEDWAB’s complex array of non-terrestrial forms, descri-

bed strictly on morphological grounds, can be accepted without opposition as

being magnetite, when no positive identification has been supplied for the

pictured structures?

From the above it would follow that the usefulness of the scanning électron

microscope in investigations of meteoritic microstructures is rather restricted,

where unknown entities are in question, since only surface morphology is

obtained. If the identity of a structure has been more or less established with

the aid of other techniques and only some additional information about surface

structure is required, then the use of SEM is obviously valuable. The combina¬

tion of SEM pictures with another analytical tool, such as the simultaneous

détermination of the elemental composition of the particle in question, can

also yield more discriminating data than microscopie images alone. For instance,

such a gross error as identifying as magnetite the small particles depicted in

fig. 22 was easily avoided. Even such combined Systems are not adéquate,

however, to provide proof of the biogenicity of an object showing simple mor¬

phology. The considérable amount of carbon occuring in the two spheroids

of fig. 17 and 18 seems to indicate that they hâve a carbonaceous matrix.

Their biogenicity now rests on their morphology, which is arguable. Such clearly

biologically appearing objects, on the other hand, as the filaments in fig. 34

could be claimed to represent recent terrestrial contaminants, had their spectra

not shown that they were thoroughly mineralized. Furthermore, the fact that

the elemental composition of the narrow filaments is different from that of the

underlying large ones makes it highly improbable that the elemental enrichment

found in these forms resulted from the HF treatment.

The issue of biogenicity.

The 1971 paper of ROSSIGNOL-STRICK and BARGHOORN (45) has

already been mentioned, in which was reported the successful isolation in rela-

tively large numbers, from the Orgueil meteorite, of what the investigators called

«hollow spheres». They applied rigorous palynological techniques to separate

the organic material from the minerai fraction, the former including the amor-

phous organic residue and organized organic structures. Although they des-

cribed several morphological types from the light microscope, their investi¬

gations were concentrated on hollow, spherical bodies only (94). Through

electron-probe microanalysis they showed that these spheres were composed

MICROSTRUCTURES IN METEORITES

219

mainly of carbon, with equivocal quantités of nitrogen, phosphorus and potas¬

sium. In 1963, when we performed our microprobe study of organized éléments

(20), instrumental limitations of the time precluded direct analysis for carbon;

therefore, these authors are the first to hâve demonstrated the organic nature

of the acid-resistant pellicles by such technique. The arguments put forth against

the possibility that the forms might be contaminants are probably acceptable

even to skeptics (at least in so far as the references is to purported abiogenic

structures), although they are almost the same as those which were advanced

aire ad y in the early 1960s. Thus, these workers hâve provided irréfutable évi¬

dence for the présence of indigenous, organized, organic microstructures in the

Orgueil meteorite.

Having shown that the objects in question were neither minerais nor contami¬

nants, there remained only one interpretive problem respecting the origin of the

forms: are they extraterrestrial microfossils or prebiological organic structures?

To deal with this «crucial question of biogenicity», the authors postulated two

types of criteria: intrinsic and extrinsic. The intrinsic criteria are familiar, being

essentially the same as those offered for many years by paleontologists working

with relatively simple fossil forms from various strata of the Precambrian (see,

for instance, in (95)): a) degree and constancy of organization;b) chemical compo¬

sition showing the presence of organics; c) abondance; and d) narrow size distri¬

bution for objects of the same type. The meteoritic «hollow spheres» satisfy

these requirements as well as many forms described from such Precambrian

strata as the South African Fig Tree Sériés (3.2 x 10 9 yr old); thus, the intrinsic

criteria for biogenicity are said to be met.

By extrinsic criteria, the authors refer to the environment from which the

forms in question originate. They discuss only one such criterion in this connec¬

tion : the necessity for a sedimentary structure. They write: «On Earth, fossils

are found only in sedimentary layers. . .» and «... there is no sedimentary

structure in the Orgueil meteorite. . .» Of the three references cited in support

of this last statement (96,35, 97), the one paper authored by scientists with

spécifie expertise in petrography (35) contains no such generalization. Further,

ROSSIGNOL-STR1CK and BARGHOORN recognized that a long-term aqueous

environment on the parent body has been admitted (98, 54), but they qualify:

«... considered at best as an interstitial filling of the accreted matrix, depositing

magnésium sulfate in the veins, too scarce to postdate an aqueous sedimentary

environment». One must ask : so considered by whom? Certainly neither of the

two references offered contains any such qualification. The authors grant that

a parallel to such «aberrant» sédiments as pyroclastic tuffs settling in water

was described for the meteorite by UREY (97) but do not deal with the impli¬

cations of this description. In addition, they fail to quote the one detailed

study on the petrography of the Orgueil stone (55). Following a sériés of refe¬

rences treating the possible presence of divine in the meteorite, which supposed-

ly argues against any aqueous stage, they conclude, in what seems to be an

almost complété non-sequitur : «Therefore, the meteoritic texture does not

conform satisfactorily with the usual sedimentary requirement associated

with true fossils». Ail of these points proving the failure of the meteorite to

provide the proper environment for fossils are dealt with in 17 condensed

220

G. CLAUS

lines, and, on this basis, the authors reached the decision that the organic micro¬

structures they studied must be abiotic (99).

In connection with the above, three points should be brought out :

1) The authors hâve reached a decision with respect to one much debated

and very important interpretive problem about the meteorite (the issue of the

biogenicity of the microstructures) by erroneously implying that two other areas

of dispute (the complex petrology of the stone versus its supposed primitive

nature and the question of whether or not the parent body ever contained a

hydrosphère) hâve been settled. In order to achieve this implication, they had to

rely on sélective and improper use of citations. What they did, in essence, was to

résolve two unknowns by fiat (there is no sedimentary structure in the meteorite

and there was no true aqueous phase), and from this concluded that the third

unknown was solved : the «hollow spheres» are not biogenic.

2) Had the investigators made the intrinsic criteria more stringent, much

of the work of the second author on Precambrian fossils would hâve been

thrown into doubt as to biogenicity. Thus, they needed a double standard,

since they were apparently unwilling even to leave open the possibility that

the Orgueil forms might be biogenic.

3) Even if one accepts their very restricted idea of the «usual sédiments»

which are possible environments for «true fossils,» the researchers uninten-

tionally confirmed that the forms found in the Lower Onverwacht Sériés (~

3.3 x 10^ yr old) - the biogenicity of which has been questioned by some

(102) and asserted by others (91, 92) - are true fossils, for these meet both

the intrinsic (103) and extrinsic criteria postulated.

In the event, once having «established» an abiogenic origin for the meteoritic

microstructures, the authors apparently felt it necessary to explain how these

forms might hâve arisen. It is not worthwhile to discuss their hypothesis in

detail, since it is rather convoluted and highly inclusive - i. e., at least fourteen

different and often mutually contradictory models of events in early solar

System history leading to the formation of carbonaceous chondrites are invoked,

without comparison of their merits. Four solid pages of text are devoted to

these theoretical considérations and to a final explanation of how the extra-

terrestrial organic spheres could hâve had an abiogenic genesis.

In 1971, it was not yet known that forms approximating the «hollow

spheres» found in the meteorite could be produced in the laboratory through

prebiotic synthesis (the work of the Indian authors mentioned earlier (32, 34)

having apparently been forgotten). Only four years after the publication of

ROSSIGNOL-STRICK and BORGHOORN’s paper, however, dramatic findings

were reported by FOLSOME et al. (104) and FRAZER and FOLSOME (105).

Utilizing a Miller-Urey type procedure, the investigators produced «massive

yields of discrète groups of highly structured morphological entities» in less

than a day (104). Among these - depicted through the use of various microscopie

methods - were bacteria-like forms, larger, more complex membrane-bound

Systems, and «hollow tubes», some of which even showed suggestions of sep-

MICROSTRUCTURES IN METEORITES

221

tation. The FOLSOME group felt that their laboratory products could explain

virtually ail of the early findings about organic structures in carbonaceous

chondrites, and that the error had been only in mistaking prebiotic forms

for biogenic fossils.

FOLSOME and his coworkers do not recognize double standards for early

terrestrial «fossils» and for those described from meteorites, and since (at least

according to their first publication) their structures meet ail the criteria of

biogenicity accepted by most specialists working on the Precambrian, it is

only natural that they question the validity of many early fossils. Their claim

that their laboratory-produced forms show more spectacular morphologies

than do many presently accepted terrestrial fossils would seem, from visual

évidence alone, to hâve some merit (106). Among findings from ancient terres¬

trial strata, they accept as unquestionably biogenic only the Transvaal Sequence

of South Africa (2.2 x 10^ yr old), in which has been discovered Petraphera

vivescenticula (107, 108), the earliest known fossil evidencing cellular diversi¬

fication. The implication, of course, is that the validity of ail work on the

Fig Tree Group (100, 101, 109-111), the Soudan Iron Formation (95, 112),

etc., is thrown into doubt, not to mention fossil discoveries in still older strata.

It would seem that ROSSIGNOL-STR1CK and BARGHOORN would hâve

two logical choices for reinterpretation of their findings in the face of this

new abiogenic synthesis work. 1) If they want to retain the original set of crite¬

ria, they would hâve to admit that the extrinsic criterion has been met for

the meteorite, since the kind of Miller-Urey synthesis employed by the FOL¬

SOME group requires the presence of liquid water. If, however, an aqueous

environment must be admitted even for abiogenesis, then the necessary condi¬

tion for the déposition and préservation of true fossils would hâve been présent

on the parent body; there would hâve been no necessity to invoke abiogenic

processes; and the organic spheres could be interpreted as biogenic. 2) If they

still wished to maintain that the meteoritic forms are abiogenic, they would

hâve to grant the inadequacy of their intrinsic criteria and accept the conclusion

of the FOLSOME group that the biogenicity of terrestrial microfossils which

areolder than 2.2 x 10^ yr is not demonstrable.

To be fair to FOLSOME et al. (104), it should be mentioned that - being

aware that there must hâve been some truly living terrestrial forms which pre-

ceded the àdvent of cellular diversification - they review non morphological

criteria for biogenicity which hâve been proposed (carbon isotope ratios; the

presence of porphyrins, even numbered fatty acids, odd numbered aliphatic

hydrocarbons, or isoprenoids; evidence of enzymatic activity; finding of opti-

cally active amino acids; etc.) and conclude that ail are unreliable for one or

another reason. We are thus left with the ultimate agnostic implication that

there is no way to prove that any simple unicellular form or filament composed

of the same type of cells found in an isolated assemblage - even if younger

than 2.2 x 10^ yr - was once living.

If the face of such a drastic situation, one might be tempted to propose

yet other approaches to the proof of the biogenicity of simple fossil forms,

but that is beyond the scope and intent of this paper.

222

G. CLAUS

Concluding remarks

The results of the investigations presented above can be interpreted from

several different standpoints. The assumption that the described forms are

représentatives of advanced prebiotic chemical synthesis would seem to be a

désirable choice, especially in view of the remarkable advances made by PERTI

(32) and BAHADUR (33, 34) in this area of endeavor. Fig. 54 of PERTI (32),

for instance, is strikingly similar to my micrograph in fig. 26, although the

chemical composition and measurements of the bodies differ. The more recent

achievements in this fîeld, such as the objects presented in the papers of FOL-

SOME and his coworkers (104, 105), do not even corne close in variety of forms

and beauty of structure to those produced with the aid of a little sunshine by

the Indian authors. However, notwithstanding some minor but bothersome

values in the publications of the FOLSOME group - such as light microscopie

pictures with asserted resolution of 0.028/im (104, fig. If), an interférence

contrast image taken at 3200 x (105, fig. 1), and so on - it may be that these

new abiotic créations mimicking biological forms hâve already solved the nagging

problem of the presence in carbonaceous chondrites of indigenous, organic

microstructures.

The fact that, according to the results of the EDAX analyses, the organized

éléments described from the SEM investigations ail contain minerais, naturally

would substantiate the view that they represent inorganic concrétions. Their

strikingly biological appearance is actually not unfamiliar to some students

of minerais, and under no conditions would it be acceptable as attesting their

biogenic origin. In effect, the remarkable array of magnetite forms described

from Type'I carbonaceous chondrites - never found before on Earth but esta-

blished basically on morphological grounds - could lend further credence to

the hypothesis that ail structures discussed above are simple minerai grains

or growths. (Elongated, dendritic types of magnetite hâve recently been added

to the shapes of this versatile minerai (12), completing the sériés needed to

identify any and every organized element as a magnetite pseudomorph, if

necessary).

Also, one can argue that the unquestionable biological «looks» of at least

the large filamentous structures make it hard to believe that they are either

minerais or the resuit of prebiotic chemical synthesis. They are therefore biotic

forms, and, as such, must represent terrestrial contaminants. The finding that

the elemental composition of the larger and smaller filaments are somewhat

different from each other but, to a certain degree similar to that of the matrix,

can best be explained by applying differential diffusion rates to them during

the period of HF etching, which process solubilized the meteorite minerais

and deposited them in the filaments. (The same process does not necessarily

hold true for the Controls. On the contrary, such discrepancies in elemental

composition between them, after treatment, might be used to prove the indi¬

genous nature of the microfossils).

As can be seen, each one of the enumerated hypothèses, or any preferered

combination thereof, can serve as a «scientific explanation» for the presence

MICROSTRUCTURES IN METEORITES

223

of highly organized microstructures in the meteorite without the necessity

of recourse to the irksome notion that they are remains of extraterrestrial

life.

«But O how dull hath Occam’s razor grown!».

I am greatly indebted to Drs. E. DEBERNARDO and K. BOLANDER, without whose

valuable help this paper could not hâve been written. Thanks are also due to Dr. S. KUNEN

and Mr. C. WAKE.

(manuscrit accepté le 10 avril 1979)

BIBLIOGRAPHY

1. CLAUS, G., NAGY, B., 1961 - Nature 192: 594.

2. CLOEZ, S., 1864 - C. R. Acad. Sci. Paris 58: 986.

3. CLOEZ, S., 1864 — C. R. Acad. Sci. Paris 59:37.

4. BOATO, G., 1954 — Geochim. Cosmochim. Acta 6: 209.

5. WIIK, H.B., 1956 - Geochim. Cosmochim. Acta 9: 279.

6. The older classification of Wiik (5) is retained in this paper, because the more recently

proposed nomenclatures of W.R. Van SCHMUS and J. A. WOOD - Geochim. Cosmo¬

chim. Acta 31: 747 (1967) - and of J.T. WASSON - Meteorites, Springer, Berlin

( 1974 ) _ do not seem essential for the understanding of the material here considered.

7. DUFRESNE, E.R., ANDERS, E., 1961 - Geochim. Cosmochim. Acta 23: 200.

8. NAGY, B., MEINSCHEIN, W.G., HENNESSY, D.J., 1961 - Abstract. Ann. Meet.

Minerai. Soc., Cincinnati, Ohio.

9. CONANT, J .B., 1947 — On Understanding Science. Yale Univ., New Haven.

10. BEVERIDGE, W.I.B., 1957 - The Art of Scientific Investigation. Norton, New York.

11. KOESTLER, A., 1959 - The Sleepwalkers. MacMillan, New York.

12. NAGY, B., 1975 — Carbonaceous Meteorites. Elsevier Scientific, Amsterdam - Oxford

- New York.

13. SAGAN, C., 1966 - in: SHKLOVSKII, I.S., SAGAN, C.: Intelligent Life in the Uni-

verse, 335. Delta, New York.

14. OVENDEN, M.W., 1972 - Nature 239: 508.

15. Van FLANDERN, T.C., 1976 - EOS 57, 4: 280.

16. ANDERS, E., 1971 - in: Physical Studies of Minor Planets, 429 (ed. T. Gehrels)

NASA SP-267.

17. FITCH, F.W., SCHWARCZ, H.P., ANDERS, E., 1962 - Nature 193: 1123.

18. FITCH, F.W., ANDERS, E., 1963 - Ann. N. Y. Acad. Sci. 108: 495.

19. ANDERS, E., DUFRESNE, E.R., HAYATSU, R., CAVAILLÉ, A., DUFRESNE, A.,

FITCH, F.W., 1964 - Science 146:1157.

20. NAGY, B., FREDR1KSSON, K., UREY, H.C., CLAUS, G., ANDERSON, C.A., PER-

CY, J., 1963 - Nature 198:121.

21. ANDERS, E., 1963 - Ann. N. Y. Acad. Sci. 108: 610.

22. VDOVYKIN, G.P., 1964 - Geokhimiya 7: 678.

23. MUELLER.G., 1964 - in: Advances in Organic Geochemistry : 119 (eds. U. Colombo,

224

G. CLA US

G.D. Hobson). Pergamon, New York.

24. FITCH, F.W., ANDERS, E., 1963 - Science 140: 1097.

25. BOSTROM, K., FREDR1KSSON, K., 1962 - Smithsonian Mise. Coll. 153, 3: 1.

26. MORRISON, P., 1962 - Science 135:663.

27. VDOVYK1N, G.P., 1962 - Geokhimiya 2:134.

28. VDOVYKIN,G.P., 1964 - Geokhimiya 4: 299.

29. VINOGRADOV, A.P., VDOVYKIN, G.P., 1964 - Geokhimiya 9:843.

30. FOX, S.W., YUYAMA, S., 1963 - Ann. N. Y. Acad. Sci. 108: 487.

31. FOX, S.W., 1965 — Nature 205: 328.

32. PERTI, O.N., 1963 - Agra Univ.J. Res. Sci. 12, 2:1.

33. BAHADUR, K., AGARWAL, K.M.L., 1962 - Proc. Natl. Acad. Sci. India 32A: 83.

34. BAHADUR, K., RANGAYANAK1, S., 1970 - J. Brit. Interplan. Soc. 23: 813.

35. ORCEL, J., ALPERN, B., 1966 - C. R. Acad. Sci. Paris 262: 1393.

36. ORCEL, J., ALPERN, B., 1967 - C. R. Acad. Sci. Paris 265: 897.

37. NAGY, B., CLAUS, G., HENNESSY, D.J., 1962 — Nature 193:1129.

38. STAPLIN, F.L., 1962 - Micropaleontol. 8:343.

39. PALIK, P., 1962 - Nature 194:1065.

40. CLAUS, G., 1968 - Ann. N. Y. Acad. Sci. 147: 365.

41. CLAUS, G., MADR1, P., 1972 - Ann. N. Y. Acad. Sci. 196: 385.

42. Van LANDINGHAM, S.L., 1965 - Nova Hedwigia 10: 161.

43. PALIK, P., 1966 - Rev. Algol. 8:89.

44. ALPERN, B., BENKHEIRI, Y., 1973 — Earth Planet. Sci. Lett. 19:422.

45. ROSSIGNOL-STRICK, M., BARGHOORN, E.S., 1971 - Space Life Sci. 3: 89.

46. CLAUS,G., NAGY, B., EUROPA, D.L., 1963 - Ann. N. Y. Acad. Sci. 108:580.

47. NAGY, B., MURPHY, T.J., MODZELESKI, V.E., ROUSER, G., CLAUS, G., HEN¬

NESSY, D.J., COLOMBO, U., GAZZARR1NI, F., 1964 - Nature 202:228.

48. SPURR, A.R., 1969 - J. Ultrastruct. Res. 26:31.

49. RUSS, J.C., 1974 - J. Submicr. Cytol. 6: 55.

50. BARGHOORN, E.S.,TYLER, S. A., 1965 - Science 147:563.

51. CLOUD, P.E., Jr., 1965 - Science 148: 27.

52. KERRIDGE, J.F., 1962 — Proc. 5th Internatl. Congr. Electron Micr. GG-5.

53. KERRIDGE, J.F., 1964 - Ann. N. Y. Acad. Sci. 119:41.

54. NAGY, B., ME1NSCHEIN, W.G., HENNESSY, D.J., 1963 - Ann. N. Y. Acad. Sci.

108:534.

55. NAGY, B., 1966 — Geol. For. Stockholm Eôrhandl. 88: 235.

56. ORCEL, J., CAII.LERE, S., BENKHEIRI, Y., 1972 - C. R. Acad. Sci. Paris 274: 9.

57. KREMP, G.O.W., 1968 — J. Brit. Interplanet. Soc. 21: 99.

58. NAGY, L.A., KREMP, G.O.W., NAGY, B.,1969 - Grana Palynol. 9:110.

59. BROOKS, J., MUIR, M.D., 1971 - Grana 11:9.

60. Van LANDINGHAM, S.L., SUN, C.N.,TAN, W.C., 1967 - Nature 216: 252.

61. JOST, M., 1965 — Arch. Mikrobiol. 50: 211.

62. FOGG, G.E., STEWART, W.D.P., FAY, P., WALSBY, A.E., 1973 - The Blue-Green

Algae. Academie, London - New York.

63. PANKRATZ, H.S., BOWEN, C.C., 1963 - Am. J. Bot. 50: 387.

MICROSTRUCTURES IN METEORITES

225

64. JEDWAB, J., 1967 — Earth Planèt. Sci. Lett. 2: 440.

65. JEDWAB, J., 1971 - Icarus 15: 319.

66. KERR1DGE, J.F., 1970 - Earth Planet. Sci. Lett. 9:299.

67. JEDWAB, J., 1965 - C. R. Acad. Sci. Paris 261: 2923.

68. Ail measurements on fine structures were read from photographically highly enlarged

pictures.

69. BOUREAU, Ed., 1977 - C. R. Acad. Sci. Paris 285:645.

70. BOUREAU, Ed., 1978 — 103e Congr. Nat. Soc. Savantes Nancy II: 9.

71. KNOLL, A.H., BARGHOORN, E.S., 1975 - Science 190: 52.

72. SCHOPF, J.W.,OEHLER,D.Z., 1976 - Science 193:47.

73. MANTEN, A. A., 1966 - Earth Sci. Rev. 1: 337.

74. NAGY,B., 1967 — Rev. Paleobot. Palynol. 3: 237.

75. ENGEL, A.E.J., NAGY, B., NAGY, L.A., ENGEL, C.G., KREMP, G.O.W., DREW,

C.M., 1968 - Science 161: 1005.

76. TAN, W.C., Van LANDINGHAM, S.L., 1967 - Geophys. J. Roy. Astro. Soc. 12:237.

77. NAGY, B., CLAUS, G., 1964 - in: Advances in Organic Geochemistry 115 (eds. U.

Colombo, G.D. Hobson). Pergamon.New York.

78. CAUMARTIN, V., 1964 - Internat. J. Speleol. 1:1.

79. BAE, H.C., COTA-ROBLES, E.H., CAS1DA, L.E., Jr., 1972 - Appl. Microbiol.

23: 637.

80. BALKWILL, D.L., CASIDA, L.E., Jr., 1973 - J. Bact. 114:1319.

81. NAGY, B., 1968 — Endeavour 18: 81.

82. NAGY, B., UREY, H.C., 1969 - Life Sci. Space Res. 7: 31.

83. SCHOPF, J.W., 1970 - J. Paleontol. 44:1.

84. KERRIDGE, J.F., MACDOUGALL, J.D., 1976 - Earth Planet. Sci. Lett. 29:341.

85. LEWIS, R.S., 1975 - in: GROSSMAN, L.: Sci. Amer. 232, 2: 30.

86. SCHOPF, J.W., 1972 — in: Exobiology 16 (ed. C. Ponnamperuma). North Holland,

Amsterdam - London.

87. BOURRELLY, P., 1970 - Les algues d’eau douce, T orne III. Boubée, Paris.

88. OBERLIES, F., PRASHNOWSKY, A. A., 1968 - Naturwissenschaften 55: 25.

89. FISHER, G.L., CHANG, D.P. Y., BRUMMER, M., 1976 — Science 192:553.

90. VOZZHENN1KOVA, T.F.,ed., 1969 - Fossil Algae of the U.S.S.R. (trans. G.K.

Beedle). Lending Libr. Sci. Techn., Boston Spa.

91. VENKATACHALA, B.S., SHARMA, K.D., 1974 - New Botanist 1:170.

92. BROOKS, J., SHAW, G., 1973 — Origin and Development of Living Systems. Aca¬

demie, London - New York.

93. LOPUCHIN, A.S., 1975 - Origin. Life 6: 45.

94. BOURRELLY, P., 1970 — Les algues d’eau douce,Tome II. Boubée, Paris.

95. BROOKS, J., MUIR.M.D., SHAW, G., 1973 - Nature 224:215.

96. For the most part, the actual results seem clear and straightforward, but there are two

points to which attention should be brought. First, it seems puzzling that in a paly-

nological study of what were apparently gram quantities of this meteorite, no truly

filamentous forms, none of the «box-like» structures, no other entities with complex

morphology were found, since the presence of such has been repeatedly described

and confirmed from Type I carbonaceous chondrites (38, 42, 43, 57-59). Secondly,

the authors flatly state that their organic spheres could not be stained with safranin.

Source : MNHN, Paris

226

G. CLAUS

This is used, on the one hand, as a démonstration that the objects are not recent

terrestrial contaminants, and on the other hand, as an indication that they are not

biogenic. Although STAPLIN (38) and one of our papers (46) are quoted - in which

publications it is clearly stated that the described objects stain with safranin - these

references are not mentioned in connection with their own négative results. Further-

more, staining with safranin is not a criterion of either biogenicity or abiogenesis.

Safranin is a simple adsorptive stain, and as such it will indiscriminately dye the most

varied substrates. One wonders why the authors’ materials hâve failed to take the

stain. Staining experiments on organized éléments with safranin and an additional 19

biological stains hâve been described at some length in (46), where the non-specificity

of this col or has been discussed in particular.

97. CLOUD, P.E., Jr., LICARI, G.R., 1968 - Proc. Natl. Acad. Sci. U.S.A. 61:779.

98. ANDERS, E., 1964 — Space Sci. Rev. 3: 583.

99. UREY, H.C., 1966 — Science 151: 157.

100. ANDERS, E., 1963 — Ann. N. Y. Acad. Sci. 108:514.

101. It should be pointed out that the implicit reasoning behind the authors’ conclusion

that the meteorite could not hâve a proper environment for the déposition of fossils

is actually the déniai of a period when the parent body would hâve a hydrosphère,

rather than the claim that the (undefined) sedimentary requirement is not met.

Space does not permit the detailed textual analysis which would be necessary to

prove this contention; however, another paper now in préparation will include a

thorough examination of this passage and other questionable generalizations in this

publication.

102. BARGHOORN, E.S., SCHOPF, J.W., 1966 - Science 152: 758.

103. SCHOPF, J.W., BARGHOORN, E.S., 1967 — Science 156:508.

104. NAGY, B., NAGY, L.A., 1969 - Nature 223: 1226.

105. NAGY, L.A., 1971 - Grana 11: 91.

106. FOLSOME, C.E., ALLEN, R.D., ICHINOSE, N.K., 1975 - Precambrian Res. 2: 263.

107. FRAZER.C.L., FOLSOME, C.E., 1975 - Origin Life 6:429.

108. By comparing photographie evidence of prebiotic forms with materials on Precambrian

structures, one has to admit that fig. 3, 21, 37, 39, 41, and 50 of PERTI (32) more

convincingly depict nuclei-like profiles than exhibited by the fossils in the micro-

graphs in fig. 50 and 51 of SCHOPF (86), or those of CLOUD and his coworkers

(fig. 39 and 40) as quoted by SCHOPF in (86). Also, one can see more details in the

prebiotic filament exhibiting incipient septation of FOLSOME et al. (106) (fig. le)

than in the microfossils shown by CLOUD and LICARI (97) (fig. 3, 5, and 6). On

the other hand, in fig. la of FOLSOME et al. (106) where the materials are supposed

to be contamination free, a nice Gloeocapsa (Cyanophyta) can be seen;while fig. 45

of PERTI (32) could easily be identified as a Cosmarium species (Chlorophyta).

109. NAGY, L.A., 1974 - Science 183: 514.

110. MACGREGOR, I.M., TRUSWELL, J.F., ERIKSSON, K.A., 1974 - Nature 245:538.

111. PFLUG, H.D., 1966 — Econ. Geol. Res. Unit., Univ. Witwatersrand, Johannesburg

Infor. Cire. 28:1.

112. PFLUG, H.D., 1967 — Rev. Paleobot. Palynol. 5: 9.

113. PFLUG, H.D., MEINEL, W., NEUMANN, K.H., MEINEL, M., 1969 - Naturwissen-

schaften 56: 10.

114. CLOUD, P. E., Jr., GRUNER, J.W., HAGEN, H., 1 965 - Science 148:1713.

MICROSTRUCTURES IN METEORITES

227

FIGURE LEGENDS

Plate 1

1: Lathe-like minerais in matrix. 2: A layer-lattice silicate flake. 3: Minerai matrix

with organic structure in center. Lines represent 0.1 /im.

Plate 2

4: Stalked object embedded in matrix. 5: Similar object found in another préparation.

6: Object of fig. 4 at higher magnification. Note the spinous wall, the stalk, and the central

vesicular profile. 7: Area of stalk; arrows point to canals or pores in wall. 8: Layering of

wall. 9: Details of vesicular structure. Microtubule-like formations at arrows. 10: Object

resembling budding yeast. Circular inclusion to the right of A, vesicles at B. 11 and 12:

Two additional organic structures. 13: Magnetite grain. Lines represent 0.1/im.

Plate 3

14: Object with massive wall. External layer of wall at black arrow. Appressed foreign

particle between white arrows. Neck canal above A. Allochtonous foreign body in wall

below B. 15: Over-exposed portion of wall to show demarkation between neck and external

object. 16: Body eut from its matrix and rotated 180° to demonstrate that originally it

was positioned in the sickle-shaped electron-luscent area in fig. 14. Lines represent 0.1/lrn.

Plate 4

17: Spheroid after HF treatment of meteorite . 18: Same as above in native stone.

19: Particle in native meteorite. 20: EDAX of above particle. 21 : Possible magnetite grains.

Note radiating spokes under A. 22: Microspheres which are definitely not magnetite.

23:Scattered magnetite microspheres. Lines represent 2/im.

Plate 5

24: Siliceous object and matrix from untreated Orgueil Specimen. 25: Similar complex

from the untreated chert. 26: Spinous object, torn from its matrix, untreated Orgueil.

Some spines retained in hole, at B. 27: Same as above, with lower magnification to show

configuration of matrix and object. A is ridge at uppermost surface of fragment; B and C,

areas where EDAX readings were taken. 28: Collapsed possible oosphère from treated

chert. 29: Dichotomously branching filament from chert. A, main filament before bran-

ching; B, front branch; C, hind branch; U, secondary branches. Ail Unes represent 2/im,

except that of fig. 29, which equals 20jUm.

Plate 6

30: Filament fragment from HF treated Orgueil. 31: Similar filament to the above,

without treatment, bridging a fissure. 32: Pencil-shaped and lathe-like filaments in un¬

treated Orgueil. A, B, and C: areas where EDAX analyses were carried out. 33: Same types

of objects as in fig. 32, but from untreated chert. A, B, and C: areas where EDAX analyses

were carried out. 34: Filamentous complex from Orgueil with bundles of broad and narrow

filaments, partially covered by recrystallized minerais of the matrix after HF treatment.

See text for meaning of labeling. 35: Detail from above complex at higher magnification,

showing the frayed sheath, a bipyramidal crystal (E) in the lumen, and the site of two

cross walls. Ail Unes equal 2/im, except that of fig. 34, which represents 20/im.

228

G. CL A US

Source : MNHN, Paris

MICROSTRUCTURES IN METEORITES

Source : MNHN, Paris

230

G. CLAUS

Source : MNHN, Paris

MICROSTRUCTURES IN METEORITES

231

Source : MNHN, Paris

232

G. CLAUS

Source : MNHN, Paris

MICROSTRUCTURES IN METEORITES

233

Source : MNHN, Paris

235

PORES IN THE APICAL CELL OF OSCILLATORIA LIMOSA AG.

Carlo ANDREIS *

ABSTRACT. - This paper deals with occurence and function of pores in the cell wall of

Cyanophyceae. The distribution model and the size of the pores could be a systematic

character.

RÉSUMÉ. - Cet article traite de la présence et de la fonction des pores dans la paroi cellu¬

laire des Cyanophyceae. La distribution et la taille de ces pores peut être dans certains cas,

un caractère systématique utile pour l’identification des Cyanophyceae.

Occurence and function of pores in the cell wall of Cyanophyceae is a pro-

blem not yet completely solved.

Plasmodesma-like structures, having about 17 nm in diameter, hâve been

observed in the cross wall of Symploca muscorum (PANKRATZ et BOWEN,

1963). Also in cross-wall of Oscillatoria princeps plasmodesma-like structures,

termed junctional pores, hâve been observed (HALFEN et CASTENHOLZ,

1971).

Pores of similar diameter hâve been described in the external cell wall of

Oscillatoria sancta, O. tenuis, O. chalibea, O. okeni and O. borneti, and also

in Microcoleus vaginatus, Porphyrosiphon notarisii and Symploca muscorum

(DRAWERT et METZNER, 1958; FRANK et al., 1962; METZNER, 1956;

RIS et SING, 1961 ; SCHULZ, 1955).

LAMONT observed that the pores reach the L 3 layer of the cell wall (LA-

MONT, 1969). On the contrary HALFEN and CASTENHOLZ observed that

they reach only the L 2 layer (HALFEN et CASTENHOLZ, 1971).

* Istituto di Scienze Botaniche delPUniversità, Via Giuseppe Colombo, 60 - 20133 Milano

(Italy).

Rev. Algol., N. S., 1979, XIV, 3: 235-238.

Source ; MNHN. Paris

236

C. ANDREIS

Fig. 1. - Apical and subapical cell of Oscillatoria limosa Ag. (x 50,000).

Source : MNHN, Paris

PORES OF OSCILLATORIA L1MOSA

237

Pores about 60 nm in diameter much bigger than the ones described before,

hâve been observed in the external cell wall of Oscillatoria princeps (RIS et

SING, 1961).

We do not know exactly how to interprète these pores, that up to now

hâve been observed only in the Hormogonales. They hâve been correlated

with mucilage sécrétion (PANKRATZ et BOWEN, 1963; WALSBY, 1968)

which, according to SCHULZ, could help these filamentous algae in the move-

ment (SCHULZ, 1955). However, according to WALSBY, SCHULZ’s interpré¬

tation is not based on experimental evidence (WALSBY, 1968). Also HALFEN

and CASTENHOLZ object this interprétation : really they proposed that the

gliding motility in the Hormogonales is caused by fibrils arranged on the surface

of L 2 layer (HALFEN et CASTENHOLZ, 1971).

Studying the ultrastructure of Oscillatoria limosa Ag. we hâve observed

the presence of pores in the external cell wall near the transversal wall, deli-

miting the apical cell from the subapical one. They are about 5 nm in diameter

and arranged in paralleî Unes about 30 nm apart. The single pores are 40 nm

apart and the Unes are 40/2nm shifted (fig. 1). This arrangement is similar

to the one described by PANKRATZ and BOWEN (1963) but it differs in size

and distribution of the pores. However the alternate disposition of pores in

neighbouring Unes completely differs from the one reported by previous Au-

thors. In the external part of the cell wall we can see pores placed in the muci-

lagenous layer.

Therefore we can find regarding the arrangement and the size of pores. The

distribution model and the size of the pores could be a systematic character.

According to FJERDINGSTAD the ultrastructural features are sometimes

diagnostic characters useful in uncertain cases for the classification of the

Cyanophyceae (FJERDINGSTAD et FJERDINGSTAD, 1976).

(manuscrit accepté le 27 mars 1979)

BIBLIOGRAPHY

DRAWERT, H. and METZNER, I., 1958 - Fluoresenz- und electronenmikroskopische

Untersuchungen an Oscillatoria borneti Zukal. V. Zellmorphologische und zellphysio-

logische Studien an Cyanophyceen. Z. Bot. 46:16-25.

FJERDINGSTAD, E. and FJERDINGSTAD, E.J., 1976 - The structure of Oscillatoria

limosa Ag. (Cyanophyceae) and the formation of hormogonia and necridia. Rev. Algol.

N. S. 11: 261-272.

FRANK, H. et al., 1962 - Elektronenoptische und chemische Untersuchungen an Zell-

wànden der Blaualge Phormidium uncinatum. Z. Naturf. 17: 262-268.

HALFEN, L. and CASTENHOLZ, R.W., 1971 - Gliding motility in the blue-green alga

Oscillatoria princeps. J. Phycol. 7: 133-145.

LAMONT, H.C., 1969 - Shear-oriented microfibrils in the mucilagineous investments

of two motile oscillatoriacean blue-green algae. J. Bact. 97: 350-361.

METZNER, I., 1956 - Zellmorphologische und zellphysiologische Studien an Cyanophy-

238

C. ANDREIS

ceen. Zur Chemie und zum submikroskopischen Aufbau der Zellwànde, Scheiden und

Gallerten von Cyanophyceen. Arch. Mikrobiol. 22: 45-77.

PANKRATZ, H.S. and BOWEN, C.C., 1963 — Cytology ofblue-green algae. I. The cells

of Symploca muscorum. Am. J. Bot. 50: 387-399.

RIS, H. and SING, R.N., 1961 — Electron microscope studies on blue-green algae. J.

Biophys. Biochem. Cytol. 9: 63-80.

SCHULZ, G., 1955 — Bewegungsstudien sowie elektronenmikroskopische Membranunter-

suchungen am Cyanophyceen. Arch. Mikrobiol. 21: 335-370.

WALSBY, A.E., 1968 — Mucilage sécrétion and the movements ofblue-green algae. Proto¬

plasma 65:223-238.

239

STUDIES ON SOUTH INDIAN SOIL ALGAE :

GLOEOCYSTIS GICAS COLLINS (TETRASPORALES)*

V.S. SUNDARALINGA, A.K.S.K. PRASAD and S. SUBBALAKSHMI**

RÉSUMÉ. - Gloeocystis gigas Collins, ordre des tétrasporales, a été observé et isolé à partir

de substrats sableux de Mahabalipuram, dans le sud de-l’Inde. Les présentes observations

réalisées sur des cultures montrent que Gloeocystis gigas est une algue palmelloïde qui se

reproduit par zoospores.

ABSTRACT. - Gloeocystis gigas Collins a member of tetrasporales has been recorded

and isolated from sandy soils of Mahabalipuram, South India. The présent observations

on culture show that the alga Gloeocystis gigas Collins is a palmelloid one and reproduces

by zoospores.

INTRODUCTION

Masses of green algae growing as palmelloid colonies exhibiting spherical

to ellipsoidal cells embedded in concentric mucilaginous sheaths, are classified

since NÂGELI’s basic work (1848) on one celled algae, as belonging to the

genus Gloeocystis Nageli. NÀGELI laid emphasis on the lack of motile repro¬

ductive cells. However, the diagnosis of the genus reproduced in the classic

Süsswasser flora of Pascher made one change that the species reproduce occa-

sionally by zoospores. Since then the genus has been conceived by later authors

differently (WEST and G.S. WEST, 1902; LEMMERMANN, 1915; FOTT

and NOWAKOVA, 1971; IYENGAR, 1971; FOTT, 1972 and HINDAK, 1978).

Thus, as HINDAK (1978) has pointed out, the genus Gloeocystis has become

an example of misinterpretation.

* Memoir N° 292 from Centre for Advanced Study in Botany.

** Centre for Advanced Study in Botany, University of Madras, Madras-600 500, India.

Rev. Algol, N. S., 1979, XIV, 3: 239-245.

Source : MNHN, Paris

240

V.S. SUNDARALINGA, A.K.S.K. PRASAD and S. SUBBALAKSHMI

Gloeocystis is one of the several algae isolated during a study on soil algae

of South India. Earlier, IYENGAR (1971) reported Gl. ampla and Gl. planc-

tonica from South India and described a new species Gl. banneergattensis.

The présent paper deals with the report of a fourth species of the genus occuring

in South India.

MATERIAL AND METHODS

Approximately 10.0 g of soil samples from Mahabalipuram were inoculated

into 250 ml. Erlenmeyer flask containing 100ml of stérile liquid modified

Bristol medium (NICHOLAS and BOLD, 1965).The flask s were then incubated

under standard conditions.

When suffîcient growth was observed (after 2-3 weeks) a portion of the

material was removed with a stérile pipette and was then centrifuged for about

5 minutes at 5000 r.p.m. to give a uniform suspension of algal cells. The sus¬

pension was then aspirated on to a plate of BBM agar. Upon illumination algal

colonies appeared from which unialgal cultures were isolated.

Colonies of different organisms, as differentiated by their colony morphology

observable with a dissecting microscope were removed from the Pétri plates

and inoculated into tubes of liquid BBM. The observations of fresh mounts

were often supplemented by using stain-crystal violet to détermine the presence

or absence of gelatinous matrices. A dilute solution was used to test the

presence or absence of starch and also to study flagellation.

Zoospores were induced when the alga was shifted from agar to liquid me¬

dium. Swarmer production was indicated by a green scum near the surface

of the water.

OBSERVATIONS

The following description is based on the study of the alga in culture (flg.

1-16).

The alga has gelatinous colonies which are bright green, hemispherical to fiat,

soft, measured about 0.01mm to 0.2 mm in diameter. The other colonies are

up to 0.25 mm. The cells are mostly spherical (rarely oblong) which are often

united and embedded in the mucilage. Cells are frequently arranged in groups

of four, each group being enclosed by a separate gelatinous and even the indi-

vidual cell envelopes are lamellated. The stratification is either concentric or

eccentric. (This is clearly observed in crystalviolet-stained material).

The cells show a thin cell wall and measure 8.3Aim-(9.13)-11.6jUm in diame¬

ter. Young cells contain a single massive cup shaped chloroplast, with a single

pyrenoid. Contracted vacuoles are not observed. Older cells measure up to

13/xm in diameter with slightly thickened walls (akinetes?) and hâve a diffuse

GLOEOCYSTIS GIGAS COLLINS

241

chloroplast completely filling the cell and contain numerous starch granules.

(At this stage pyrenoid is not distinguishable). Multiplication or végétative

reproduction is by means of formation of 2-4 daughter cells, which secrete

individual envelopes later.

Asexual reproduction is by the production of biflagellated zoospores which

are of Chlamydomonas type. Zoospores are mostly spherical, rarely oblong,

measuring 5Aim-8.3/im (6.3) in diameter. Flagella are equal, the length of the

flagellum is twice as long as the body of zoospore. Zoospores possess a cup-

shaped chloroplast with a single pyrenoid and a distinct eye spot is also obser-

ved. Papilla is not observed.

Sexual reproduction has not been observed.

DISCUSSION

The présent alga resembles tetrasporalean généra Gloeocystis Nag., Sphae-

rellocystis Ettl. and Chlamydocapsa Fott. Tetrasporalean algae differ from the

coccoid ones in the presence of contractile vacuoles. Sphaerellocystis (ETTL,

1960) and Chlamydocapsa Fott (FOTT, 1972) possess contractile vacuoles,

lt is not clearly known whether the type species of Gloeocystis and the other

species hâve them. However, 1YENGAR (1971) observed 1 or 2 contractile

vacuoles in Gl. ampla. NOVAKOVA (1964) transfers this species to Sphaerello¬

cystis as S. ampla since the structure of the cell is tetrasporine. Gloeocystis

Nag. includes species lacking contractile vacuoles. The présent alga resejnbles

more closely these species in having the cells grouped in colonies-exhibiting

a palmelloid habit, a stratified gelatinous envelope , a cup shaped chloroplast

with a pyrenoid and in the absence of contractile vacuoles. It differs from

Sphaerellocystis in having a palmelloid condition and in the absence of contrac¬

tile vacuoles and from Chlamydocapsa mainly in the absence of contractile

vacuoles. The présent alga resembles otherwise to one species of Sphaerello¬

cystis (S. globosa) which does possess a mucilaginous covering. Naturally one

could expect this species to form palmelloid colonies under certain conditions.

Thus the présent alga is assigned to the genus Gloeocystis.

It is quite probable that many species presently included in this genus are

merely palmelloid stages of other motile algae. IYENGAR (1971) retained the

genus in the Tetrasporales, rightly pointed out that some species of Chlamydo¬

monas are known to get into a palmelloid condition or « Gloeocystis condition»

and unless one investigates the organism fully, it is difficult to décidé whether

it is a Gloeocystis or a Chlamydomonas in a « Gloeocystis stage». It is rather

difficult to draw the line of démarcation between a Chlamydomonas in Gloeo¬

cystis stage and a Gloeocystis. One does not know whether it is proper to

reduce ail species of Gloeocystis to species of Chlamydomonas which spend

most of their time in palmelloid condition to either Gloeocystis or Palmella

species (IYENGAR, 1971). It may be worth mentioning that young colonies

of Hormotila hâve much the same appearance as Gloeocystis and each of the

242

V.S. SUNDARAL1NGA, A.K.S.K. PRASAD and S. SUBBALAKSHMI

spherical cells is enclosed in a thick layered gelatinous envelope. Observations

for a sériés of years of Gl. vesiculosa and Gl. rupestris hâve shown great unifor-

mity (COLLINS, 1909). The présent observations in culture showed that the

présent alga is a palmelloid one.

LEMMERMAN (1915) conceived this genus in a broad sense and referred

six species to it. They are Gl. planctonica (W. et G. S. West) Lemmermann,

Gl. vesiculosa Nàg., Gl. botryoides Nâg., Gl. rupestris (Lyngb.) Rabenh., Gl.

ampla Kiitz. and Gl. major Gerneck. Gl. vesiculosa N'aig. is the type. COLLINS

(1909), besides the type and Gl. rupestris, recognized five species. They are

Gl. gigas, Gl. fenestralis, Gl. parotiniana, Gl. zostericola and Gl. scopularum.

The latter two species are marine. HEYING (1962) described a species, Gl.

hercynica. MAINX (1928) described a species Gl. maxima which is a latter

homonym of Gl. maxima Gutwins. Therefore, DESIKACHARY (in IYENGAR,

1971) renamed it as Gl. mainxii. IYENGAR (1971) while reporting the indian

records for Gl. ampla and Gl. planctonica, described a new species Gl. banneer-

gattensis. HINDAK (1978) besides the type species Gl. vesiculosa Nâg., included

one more species Gl. polydermatica (Kiitz.) Hindak. The distinction among

the species of Gloeocystis is based on the shape of the cells and cell dimensions.

The présent alga cornes very close to Gl. gigas Collins and therefore it is

placed under this species. The alga also resembles Gl. vesiculosa but differs

slightly in having generally larger cells 8-11.6A(m in diameter. LEMMERMANN

(1915) indicated reproduction by zoospores in three species, Gl. vesiculosa, Gl.

ampla and Gl. major. The présent observations show that Gl. gigas also repro¬

duces by zoospores.

ACKNOWLEDGEMENTS

The authors are thankful to Prof. T. V. Desikachary for his comments and for critically

going through the manuscript and to Prof. M.S. Balakrishnan for his suggestions. The finan-

cial assistance from the University Grants Commission of India for one of the authors

(A.K.S.K.P.) is gratefully acknowledged.

(manuscrit accepté le 8 septembre 1979)

REFERENCES

BISCHOFF, H.W. and BOLD, H.C., 1963 — Some soil algae from Enchanted Rock and

related algal species. Phycological Studies IV. Univ. of Texas Publi. n° 6318. Austin,

Texas.

COLLINS, F.S., 1909 — The green algae of North America Tufts College. Studies Sériés

2: 79-480.

ETTL, H., 1960 — Die Algenflora des Schonesgestes. Nova Hedwigia 2: 509-546.

FOTT, B., 1972 — Chlorophyceae, Ordnung Tetrasporales, In : Die Phytoplankton des

Süsswassers, Systematik und Biologie, G. HUBER-PESTALOZZI ed.,Teil 6: 1-116.

FOTT, B. and NOVAKOVA, M., 1971 — Taxonomy of the palmelloid généra Gloeocystis

GLOEOCYSTIS GIGAS COLLINS

243

Nâg. and Palmogloea Kiitz. (Chlorophyceae). Arch. Protistenk 113: 322-333.

HINDAK, F., 1978 - The genus Gloeocystis (Chlorococcales Chlorophyceae). Preslia

50:3-11.

1YENGAR, M.O.P., 1971 - Contributions to our knowledge of South Indian Algae IV.

Phykos' 10(1 & 2): 147-151.

LEMMERMANN, E., 1915 - Tetrasporales. In : Die Süsswasser-flora, Pascher ed., Iena, 5:

21-51.

MAINX, F., 1928 - Einige neue Chlorophycean Tetrasporales und Protococcales. Arch.

Protistenk 61 (1/2): 1-288.

* NÂGELI, G., 1849 - Gallungen ein zelliger Algen. Zürich : 139 p.

NOVAKOVA, M., 1967 - Asterococcus Scherffel and Sphaerellocystis Ettl, two généra

of palmelloid green algae. Acta Univ. Carol. Biol. 2:155-166.

WEST, W. and WEST G.S., 1902 - A contribution to the fresh water algal of Ceylon.

Trans. Linn. Soc. (Bot.) 26:123-215.

* Original not seen.

Plate I : fig. 1-10

Gloeocystis gigas Collins. - 1 : Thallus organization at low magnification (crystaj violet

stained) ca. x 140. 2 & 3: Végétative cells in colonies (note the individual envelope and the

common envelopes) (crystal violet stained) ca. x 550. 4: Cells showing concentric lamella¬

tions of the mucilage envelope (crystal violet stained) ca. x 770. 5 : Biflagellated zoospores

(lodine stained) ca. x 1000. 6: A zoospore at higher magnification (note the eyespot) ca.

x 1600. 7: Végétative cells stained with lodine, ca. x 780. 8: Old cells showing numerous

starch granules (lodine stained) ca. x 780. 9: A mature diad (lodine stained) ca. x 1200.

10: Stratified envelopes without the cell (crystal violet stained) ca. x 1200.

Plate 2 : fig. 11-16

Gloeocystis gigas Collins. — 11: A portion of the thallus at low magnification. 12:

An enlarged portion of the végétative cells in colonies (note the individual and the common

envelopes). 13: Colony of 4 cells (note the individual and the common envelopes). 14:

Cells embedded in lamellated sheaths. 16: Biflagellated zoospores.

Fig. 11: scale = 50/im; fig. 12-16: scale = 10/im.

244

V.S. SUNDARALINGA, A.K.S.K. PRASAD and S. SUBBALAKSHMI

Source : MNHN, Paris

GLOEOCYSTIS GIGAS COLLINS

245

Source : MNHN, Paris

247

PARADOXIA PELLETIERI, NOV. SP.

NOUVELLE ESPECE DE CHLOROCOCCALES DE FRANCE

(CHLOROPHYCEAE)

J.C. DRUART et O. REYMOND**

RÉSUMÉ. - Les auteurs décrivent une nouvelle espèce de Chlorophycée du genre Paradoxia

récoltée au lac du Bourget (Savoie, France). Cette algue est toujours unicellulaire. Son pôle

antérieur est effilé et porte une ancre peu visible. Le pôle postérieur est arrondi. La cellule

porte des soies, principalement sur la partie postérieure.

SUMMARY. — The authors describe a new species of Chlorophyceae of the genus Para¬

doxia found in the lac du Bourget (Savoie, France). This alga is always single-celled; its

anterior pôle is sharp and surmounted with a hardly visible anchor. Some setae surround

the cell, particularly at the posterior end.

Au cours de prélèvements faits sur le lac du Bourget (Savoie), l’observation

du matériel planctonique recueilli de juillet à septembre 1978 nous a fait décou¬

vrir un organisme non encore décrit, et que nous proposons de nommer Para¬

doxia pellet ieri (fig. 1).

Cet organisme est toujours unicellulaire. Les cellules sont fusiformes et

hétéropolaires. Le pôle antérieur (voir la terminologie employée pour Ankyra

par SWALE et BELCHER, 1971) est effilé, et son extrémité est bien visible

au contraste de phase. Cette extrémité porte une ornementation très faiblement

* I.N.R.A. Station d’Hydrobiologie Lacustre, 75, Avenue de Corzent, 74203 Thonon-les-

Bains (France).

** Université de Genève. Département de Biologie Végétale. Laboratoire de Microbiologie

générale, 3 Place de l’Université, CH 1211 Genève 4 (Suisse).

Rev. Algol., N. S., 1979, XIV, 3: 247-252.

Source : MNHN, Paris

248

J.C. DRUART et O. REYMOND

Fig. 1. - Paradoxia pelletieri nov. sp. Quatre cellules A, B, C, D.

contrastée qui, en coupe optique, a la forme d’une ancre souvent à peine visible

(fig-l.D).

Cette ancre pourrait être identique à celle observée par KISSELEV (1955)

chez Ankyra calcarifera (Kisselev) Fott (1957) (fig. 2), ou décrite et dessinée

par SMITH (1916), FOTT (1974) et REYMOND (1979) chez Ankyra judayi

(Smith) Fott (1957) (fig. 3, 4 et 7).

Il faut noter que les organismes des genres Paradoxia Swirenko (1928) et

PARADOXIA PELLETIERI NOV. SP.

249

Fig. 2. - Ankyra calcarifera (Kisselev) Fott (dessin d’après Kisselev, 1955). Fig. 3. - An-

kyra judayi (Smith) Fott. Smith (1916) décrit le pied comme un disque, et non des

appendices en forme d’ancre (voir Fig. 7) (dessin d’après Smith, 1916). Fig. 4. — Ankyra

judayi (Smith) Fott. Cellule de culture. Le pied, bien que représenté par des appendices

en forme d’ancre, est en réalité un disque plus ou moins aplati (voir fig. 7) (dessin d apres

Fott, 1974).

Ankyra Fott (1957) sont généralement surmontés d’une ancre. Cette dernière

peut être de deux types. Elle est formée soit par deux appendices foliacés (fig. 5

et 6), possédant une ultrastructure en lame très particulière (SWALE et BEL-

CHER, 1971; REYMOND, 1979), soit par un disque fait de fibrilles rayonnant

à 360° (fig. 7) et ne s’aggrégeant pas en un tissu comme dans le cas précédent

(les fibrilles formant ce disque s’agglomèrent quelquefois entre elles et forment

un appendice, dit en queue de cheval, REYMOND, 1979).

Le pôle postérieur est arrondi, comme chez Paradoxia multiseta Swirenko

(1928) (fig. 6). Une dizaine de soies environ recouvrent le corps cellulaire.

Elles sont plus contrastées et plus serrées que sur le pôle postérieur de la cellule.

Vers l’extrémité antérieure de l’algue, les soies sont perpendiculaires à 1 axe

cellulaire, et sont parfois doubles (fig. 1 C). Le contraste de phase est indispen¬

sable pour leur examen.

250

J.C. DRUART et O. REYMOND

Fig. 5. — Ankyra paradoxioides Cirik. On remarque la présence de soies sur toute la cellule.

Les deux appendices antérieurs sont foliacés et bien distincts (matériel fourni par Mme

Cirik). Fig. 6. - Paradoxia multiseta Swirenko. Une seule cellule est représentée en

entier. Les appendices foliacés de chacune des cellules se croisent avec un angle de 90°.

Les cellules ne sont accrochées entre elles que par leur apex (résultats optiques et élec¬

troniques) (matériel provenant du lac de Bret près de Lausanne, Suisse, et récolté en

septembre 1976). Fig. 7. — Représentation schématique faite à partir d’observations en

microscopie optique et électronique d’apex de Ankyra judayi. On ne trouve plus une

organisation foliacée (fig. 5 et 6) mais des fibrilles peu organisées, formant un cône

plus ou moins aplati (REYMOND, 1979). L’appendice antérieur de Paradoxia pelletieri

a probablement une structure identique.

Le corps cellulaire mesure de 18 à 22/im de long, et de 3 à 4£im de large

(sans soies, ni ancre). Les soies atteignent 15 Hm de longueur. La largeur de

l’ancre est de 7 /Jim.

PARADOXIA PELLETIERI NOV. SP.

251

Les cellules possèdent un plaste important, avec un pyrénoïde (rarement

deux). Le noyau est généralement placé en position légèrement antérieure et

latérale.

A la suite de recherches faites au microscope électronique par SW ALE et

BELCHER (1971) sur Ankyra, et par REYMOND (1979) sur Paradoxia et

Ankyra, il s’est révélé que la frontière entre les deux genres était très ténue.

C’est pourquoi par la présence de soies, d’un pôle arrondi et malgré l’absence

de cénobes, l’organisme que nous décrivons se rapproche plus de Paradoxia

Swirenko (1928) que de Ankyra Fott (1957).

Paradoxia multiseta Swirenko (1928) (fig. 6), Ankyra calcarifera Kisselev

(1955) (fig- 2), et Ankyra paradoxioides Cirik (1978) (fig. 5) sont proches

de notre nouveau taxon, mais s’en différencient par la présence d’appendices

antérieurs foliacés et nettement visibles (fig. 5 et 6), de cénobes (fig. 6), de

parties cellulaires postérieures plus ou moins effilées (fig. 2 à 5), d’épines antéro¬

latérales épaisses non perpendiculaires à l’axe de l’algue (fig. 2 et 5), et d axes

cellulaires légèrement recourbés (fig. 2).

Paradoxia pelletieri a été recueillie au moyen d’un appareil permettant

un prélèvement intégré (brevet INRA, 1978) dans la couche d eau allant de la

surface à 10 m de profondeur. Elle coexistait avec les Chlorophycées suivantes :

Ankyra judayi (Smith) Fott, Ankyra spatulifera (Korschikov) Fott, Scenedes-

mus ecornis Chodat, Oocystis solitaria Wittrock. Cet organisme a été trouvé

dans le plancton pélagique, mais il n’est pas impossible qu’il soit également

benthique, son appendice antérieur servant alors d’organe de fixation. L’abon¬

dance de cette nouvelle espèce est restée très faible durant la période citée,

environ une cellule par millilitre.

Les plages de variations des principaux paramètres physico-chimiques de

l’eau, de juillet à septembre 1978, période de développement de cette algue,

sont récapitulées dans le tableau suivant :

Temp.

TAC

SO 4

NO 3

PO 4

P. total

°C

mg /1

mé /1

mg /1

mg P/l

minimum 16 3

8,2

33,6

3,8

1,90

15,3

0,009

0,039

maximum 22 ° 8

8,2

50,2

5,8

2,74

17,9

0,26

0,018

0,059

Le cycle de reproduction de Paradoxia pelletieri n’est pas encore connu.

Diagnose latine :

Cellula fusiformis, solitaris, libéra, heteropolaris (L = 18-22pm, l — 3-4pm).

Unus polus ornatus processus insignificanti in coni forma qui anchora similis

est. Apex poli qui hanc appendicum fert dilucidissimus est. Alter polus rotundus

est. Cellula tenuissimis radiantibus setis ornata, maxime in posteriori polo.

Chromatophorus unum centralem pyrenoidum fert. Iconotypus: fig. 1 (A, B,

C, D). Locus classicus: lacu burgetense (Gallia).

252

J.C. DRUART et O. REYMOND

Nous remercions le professeur BOURRELLY qui nous a fait bénéficier de son expé¬

rience et nous a encouragé à publier cet article.

(manuscrit accepté le 22 février 1979)

RÉFÉRENCES BIBLIOGRAPHIQUES

CIRIK, S., 1978 - Ankyra paradoxioides. Nouvelle espèce de chlorococcales de Turquie

(Chlorophyceae). Revue algologique XIII, 3: 207-210.

FOTT, B., 1957 — Taxonomie der Mikroskopischen Flora einheimischer Gewàsser. Preslia

29: 278-314.

FOTT, B., 1974 — Taxonomische Übersicht der Gattung Ankyra Fott 1957 (Characiaceae,

Chlorococcales). Preslia (Praha) 46: 289-299.

KISSELEV, I.A., 1955 - De specie nova generis Lambertia Korsch. e stagnis regionis

krasnodar. Not. Syst. sect. Cryptogam. Inst. Bot. Acad. Sc. U.R.S.S., Moscou, 10: 39-40.

REYMOND, O., 1979 — Étude morphologique et systématique des genres Paradoxia et

Ankyra (Chlorococcales). Sch. Z. für Hydrologie 40, 2: 350-357.

SMITH, G.M., 1916 — New or interesting algae from lake of Wisconsin. Bull. Torrey Bot.

Club, Lancaster, Pa., 43: 471-483.

SWALE, E.M.S. and BELCHER, J.H., 1971 — Investigation of species Ankyra Fott by

light and Electron Microscopy. Phycol. J. (1971) 6,1: 41-50.

SWIRENKO, D., 1928 — Recherches sur la flore algologique de la rivière Ingouletz. Arch.

Russ. Protistol., Kijev., 7: 25-74.

L’ÉVOLUTION DE LA STRUCTURE CLADOMIENNE

chez les CHARALES et les CÉRAMIALES

Étude comparative

253

Marius CHADEFAUD*

RÉSUMÉ. - Le thalle des Chara est formé de cladomes à phyllidies, non à pleuridies,

cela au terme d’une évolution qui a conduit de cladomes à pleuridies ( Draparnaldiopsis) à

des cladomes à phyllidies de type simple (Nitella), puis à des cladomes à phyllidies de type

complexe (Chara). Une évolution analogue mais toutefois non identique, se retrouve chez

les Céramiales.

SUMMARY. - The thallus of the Chara is composed of cladoms with phyllidia, not with

pleuridia. This is the resuit of an évolution which led from cladoms with pleuridia (Drapar¬

naldiopsis) to cladoms with phyllidia of a simple type (Nitella), then to cladoms with

phyllidia of a complex type (Chara). An analogous évolution, but not identical, is to be

found in the Céramiales.

Parmi les Algues vertes, les Charales sont particulièrement intéressantes,

parce que ce sont les plus évoluées des «Chorophycées à phragmoplastes»,

lesquelles sont, selon P1CKETT-HEAPS et MARCHANT (1972) les plus proches

des plantes supérieures (cf. CHADEFAUD, 1976 et 1977).

Elles ont fait l’objet de nombreux travaux, dont les plus récents et les plus

précis sont ceux de SUNDARAL1NGAM (1954, 1960 : étude morphologique)

et de DUCREUX (1974: morphogenèse, étude expérimentale). En 1960, nous

leur avions attribué une structure cladomienne, en supposant leur thalle formé

de cladomes uniaxiaux, garnis de verticilles de pleuridies. Aujourd’hui, nos

idées sur les cladomes ayant évolué, notamment grâce aux travaux de Mmes

L’HARDY-HALOS (1966 à 1975) et ARDRÉ (1967a, 1967b; GINSBURG-

ARDRÊ, 1964, 1966), nous avons modifié cette interprétation, en constatant

* Laboratoire de Cryptogamie du M.N.H.N., 12 rue Buffon, 75005 Paris.

Rev. Algol., N. S., 1979, XIV, 3: 253-273.

Source : MNHN, Paris

254

M. CHADEFAUD

que les verticilles des Chara et Nitella sont constitués de phyllidies, et non de

pleuridies.

Rappelons ici que, d’une façon générale, les cladomes uni-axiaux sont formés

d’un filament axial ( Oc ) garni sur ses flancs, soit de pleuridies (7T), composées de

filaments pleuridiens, soit de phyllidies (<p), composées de filaments phyllidiens

(v. CHADEFAUD, 1960). Le filament axial a une croissance indéfinie, assurée

par une cellule initiale apicale. Les filaments phyllidiens (/3 1, porteurs des P 2,

porteurs à leur tour des P 3) et les filaments pleuridiens n’ont au contraire

qu’une croissance définie, parce que leur initiale cesse vite de fonctionner. Mais

les filaments phyllidiens, contrairement aux pleuridiens, constituent des «bra-

chyblastes» c’est à dire des systèmes de petits cladomes, ou «brachycladomes»

réduits chacun à son axe, et nés les uns des autres. Autrement dit, dans une

phyllidie, les filaments P sont en réalité les filaments axiaux (à croissance limi¬

tée) de brachy-cladomes, formant un brachyblaste de formule : un P 1 + des

P 2 + des P 3, etc.

Ces données étant rappelées, nous allons montrer comment elles s’appliquent

aux Charales, et ensuite comparativement aux Céramiales, de l’étude desquelles

d’ailleurs elles proviennent (CHADEFAUD, 1954). Nous observerons ainsi,

dans ces deux groupes pourtant non apparentés, une évolution de la structure

cladomienne, rattachable à un même modèle fondamental.

A. - CHARALES

Nous prendrons comme point de départ, pour suivre l’évolution de leur

structure cladomienne, le Draparnaldiopsis indica Bharad., qu’on ne range pas

parmi les Charales, mais qui nous paraît être une «Proto-Charale», encore

planogame et digénétique, tandis que les Charales sont oogames et monogéné¬

tiques. Cela dit :

Fig. 1. - Draparnaldiopsis indica. - Cladome à pleuridies. Axe cladomien((a), avec sous-

segments nodaux (n) et internodaux (in); sur les nodaux, cycles de quatre pleuridies

(TT).

CHARALES ET CÉRAMIALES

255

a) Le Drapamaldiopsis (fig. 1) est formé de cladomes à pleuridies, compre¬

nant chacun: 1. un filament axial (a), dont chaque segment est subdivisé en

un sous-segment nodal (distal et court) et un sous-segment internodal (proximal

et long), qui ne se cloisonnent ni l’un ni l’autre; 2. des pleuridies (ff), insérées

sur les sous-segments nodaux, en un verticille de quatre sur chaque sous-segment.

b) Les Nitella (fig. 2), Charales qu’on considère comme peu évoluées, sont

au contraire formés de cladomes à phyllidies. Chez eux, il n’y a plus de pleuri¬

dies: n’existent que des filaments axiaux constitués, comme ceux du Drapar-

naldiopsis, de segments subdivisés chacun en deux sous-segments, l’un nodal,

l’autre internodal. De plus, une hiérarchisation fait que certains de ces filaments

axiaux sont des filaments caulidiens (= simulant des tiges) à allongement indé¬

fini, et les autres des filaments phyllidiens, moins gros que les caulidien, et à

croissance limitée. Dans le filament caulidiens (a) les sous-segments nodaux,

au lieu de rester indivis, se subdivisent en cellules centrales entourées de péri-

centrales (fig. 2 B), et sur chacune de celles-ci se développe un filament phylli-

dien primaire (0 1); de même, sur les nodaux de ce phyllidien primaire naissent

les phyllidiens secondaires (0 2), etc. Les 01,0 2, etc., sont des axes de brachy-

cladomes, et l’ensemble de chaque 01, avec ses 0 2, 0 3, etc..., forme une

phyllidie (i£) (fig. 2 A).

Fig. 2. — Nitella : Cladome à phyllidies (schéma). — A: Axe caulidien (Oi), avec sous-seg¬

ments nodaux (n) et internodaux (in); sur chaque nodal, verticille de phyllidies (ifl) for¬

mées d’un axe phyllidien (0 1) porteur d’axes phyllidiens (02); B: Coupe transversale

schématique d’un sous-segment nodal formé de cellules centrales (encore non redmsees)

et de cellules péricentrales; C: Développement d’un axe 0 1 à partir d’une des péricen-

trales de OC.

Ainsi, du type Drapamaldiopsis au type Nitella, l’évolution a comporté,

corrélativement: 1. la suppression des pleuridies; 2. la hiérarchisation des fila¬

ments axiaux, devenant les uns caulidiens (tt), les autres phyllidiens (0 1, 0 2...);

256

M. CHADEFAUD

3. La disposition coordonnée des phyllidiens pour former les phyllidies (<p).

D’après cela, du moins chez les Charales, les phyllidies ne sont pas des pleuri-

dies évoluées : phyllidies et pleuridies sont des formations différentes, et la

formation des phyllidies est en corrélation avec la suppression des pleuridies.

c) Les Chara (fïg. 3 à 6), plus évolués que les Nitella, ont une organisation

analogue, mais plus complexe et plus sophistiquée. On retrouve chez eux des

axes cladomiens, à segments subdivisés en sous-segments internodaux et nodaux,

ceux-ci cloisonnés en centrales et péricentrales (fig. 3, 4 et 5), mais il y a (fig. 3

et 4) :

Fig. 3. - Chara : cladome à phyllidies (schéma). - Axe caulidien (û:) avec sous-segments

internodaux (in) et nodaux (n), ceux-ci subdivisés en cellules centrales (en noir) et péri¬

centrales. — Axes phyllidiens (P 1): un verticille sur chaque sous-segment nodal de Ci ;

segment coxal dérivé d’une pericentrale de tt, et subdivisé en un sous-segment internodal

(in) et un sous-segment nodal (n); autres segments constitués comme ceux de û! (cellules

centrales en noir). - Axes phyllidiens P 2 corticants [P 2 C): nés des péricentrales du

sous-segment nodal des segments coxaux de P 1, ils sont les uns ascendants, les autres

descendants, et cortiquent a. Axes phyllidiens P 2 réduits à une penne {P 2 p), nés des

péricentrales des sous-segments nodaux des autres segments de P 1 (un verticille sur

chacun de ces sous-segments) segment coxal dérivé d’une de ces péricentrales, et sub¬

divisé en un sous-segment internodal (in) et un sous-segment nodal (n); le reste réduit

à une penne. — Axes phyllidiens P 3 corticants (P 3 C), nés des sous-segments nodaux

des segments coxaux des P 2 p, ils sont les uns ascendants, les autres descendants, et

cortiquent les p 1. Phyllidie = P 1 + les P 2 + les P 3.

- des a caulidiens; ils sont «orthotropes» (DUCREUX, 1974);

sur chaque nodale de ceux-ci, un verticille de P 1; ils sont «plagiotropes»,

et terminés par des segments «imparfaits», ce qui est en rapport avec leur allon¬

gement défini (v. plus loin);

- sur le segment coxal des P 1, deux p 2 corticants (P 2 C), l’un ascendant,

l’autre descendant, appliqués sur le tt;

CHARALES ET CÉRAMIALES

257

- sur les autres sous-segments nodaux des (3 1, un verticille de P 2 réduits à

des «pennes» (0 2 p);

- sur le segment coxal de chacune de ces pennes, deux P 3 corticants (P 3 C),

l’un ascendant, l’autre descendant, appliqués sur le P 1 ;

- sur les sous-segments coxaux des P corticants, deux P corticants secondaires

((3 C’), qui ont valeur de (3 3 sur les corticants P 2, et de (3 4 sur les corticants P 3

(fig. 5,^ et C 2 ).

De plus, les sous-segments coxaux des P 2 portent deux «stipulodes» (fig. 5A)

et les sous-segments nodaux des (3 corticants deux «acicules» (fig. 5C). Celles-ci

sont peut-être les stipulodes de (3 abortifs, qui auraient valeur de 0 3 sur les

0 2 corticants, de P 4 sur les corticants 0 3.

On notera en outre :

1. Que sur le filament caulidien a, le mode de cloisonnement des sous-

segments nodaux, donnant les péricentrales, indique une bilatéralité du segment,

marquée dès le début par la position de la première cloison, a - b (la disposition

des cloisons suivantes rappelle celle des cloisons séparant les péricentrales des

Polysiphonia) (fig. 5 B);

2. Que d’après l’orientation de la cloison a - b sur les sous-segments nodaux

successifs, l’axe cladomien a. possède une infra-structure hélicoïdale (on peut

la rapprocher de celle qu’indique la disposition hélicoïdale des phyllidies des

Polysiphonia) (fig. 10B);

3. Que sur les filaments axiaux caulidiens (a) les péricentrales deviennent

les segments coxaux des P 1 ; de même sur ceux-ci les péricentrales deviennent

les segments coxaux des (3 2, etc... Ces segments coxaux, comme les autres,

se subdivisent en un sous-segment internodal et un sous-segment nodal, celui-ci

à son tour cloisonné en centrales et péricentrales (fig. 3 et 4) ;

4. Qu’à partir du zygote générateur, le premier cladome, qualifie (a tort)

de «protonémien», a une organisation plus simple que les suivants. Chez le

Chara vulgaris, il est formé de deux segments non cortiqués, encore subdivisés

en un demi-segment internodal et un nodal, puis d’une sérié de segments impar¬

faits, non subdivisés, à l’extrémité de laquelle la cellule initiale, cessant de

fonctionner, devient elle-même un tel segment. Sur le noeud du premier seg¬

ment naissent des rhizoïdes, sur celui du second, un cycle de P 1, sans pennes

ni cortex (fig. 6 A).

5. Enfin, que les (3 1 normaux se terminent comme le filament a «protoné¬

mien», par des segments imparfaits (fig. 4)*, que le segment coxal des 0 corti¬

cants se cloisonne autrement que les autres, pour former un petit massif paren¬

chymateux (k), d’où partent des rhizoïdes (lesquels sont peut-être des P très

simplifiés) (fig. 5 A 2).

* Cela montre que les (3 sont bien de même nature que les G, malgré leur allongement

défini.

258

M. CHADEFAUD

Source : MNHN, Paris

CHARALES ET CÉRAMIALES

259

Fig. 4 - Chara : phyllidie. - A - Sur un axe caulidien (a) développement des axes phylli-

diens (0 1): sous-segments internodaux (in) et nodaux (n) de l’axe Oi, puis du segment

coxal de /3 1 , puis des autres segments de 0 1 ; segment coxal de 0 1 , dérivé d’une péri-

centraie de 0i\ dans les sous-segments nodaux, centrales en noir; ss, segments imparfaits

constituant la partie distale de 0 1. - B - Sous-segment nodal de 0 1, avec cellules cen

traies (en noir) et péricentrales, celles-ci devenues les segments coxaux des 0 p (pennes)

subdivisés en un sous-segment internodal (in) et un sous-segment nodal (n) ; sur ce der

nier, axes phyllidiens corticants (0 3 C). - C - Phyllidie adulte, avec segments de 0 1 par

faits, revêtus d’axes corticants (0 3 C) et garnis de verticilles de pennes (0 2 p), et seg

ments imparfaits (ss).

Fig. 5- - Chara : sous-segments nodaux des axes phyllidiens (schéma). — Al - Axe 01,

sous-segment nodal coxal: centrale et péricentrales; axes corticants 0 2 C et stipulodes

s t. — A2 - id.: sous-segment nodal coxal en pointillé; st, stipulodes;0 2 C, axes corticants,

l’un descendant, l’autre ascendant. De celui-ci, le premier segment (k) est parenchyma¬

teux. - B1 - Axe 0 1, sous-segment nodal normal: centrales et péricentrales; ordre des

cloisonnements séparant les péricentrales; axes 02 p indiqués par des flèches. — B2 -

id.; axes 0 2p réduits à des pennes, avec segment coxal dérivé d’une péricentrale de 0 1,

et subdivisé en un sous-segment internodal (in) et un sous-segment nodal (n) ; sur celui-

ci (en noir), départ d’axes corticants 0 3 C. — Cl - Axe corticant (0 C) : centrale (en noir) ;

péricentrales latérales portant des axes corticants supplémentaires (0C\ insertions en

noir) ; péricentrale externe portant deux acicules (ac) ; elle devrait aussi porter un axe

0’, mais il ne se développe pas. - C2 - Idem - pe, péricentrale externe ;ac, acicule;0C’ ,

axe corticant supplémentaire.

Quant à la formation de cladomes axillaires, dans l’aisselle des phyllidies

du cladome principal, ils sont engendrés par une péricentrale de celui-ci, de

laquelle dérivent, d’abord le filament 01 de la phyllidie, ensuite le filament

axial OL' du cladome axillaire (fig. 6B). Celui-ci demeure d’ailleurs généralement

à l’état de bourgeon, du fait d’une action inhibitrice émanant de l’apex du cla¬

dome principal (DUCREUX, 1974), et il est flanqué de deux bourgeons axil¬

laires accessoires.

Pour la situation des organes reproducteurs, v. la fig. 6, C et D : les organes

mâles terminent des 0 2, et les organes femelles des 0 3, ceux-ci homologues

à des 0 3 corticants. T

Ainsi, les Chara montrent que les cladomes à phyllidies, dépourvues de

pleuridies et entièrement formés de filaments cladomiens axiaux (a, puis 01,

0 2...), homologues à ceux du Drapamaldiopsis , peuvent évoluer vers un type

complexe, comportant des différenciations importantes. Comme ces algues

sont des Chlorophycées «à phragmoplastes», et que celles-ci semblent appa¬

rentées aux plantes supérieures ou Cormophytes, on peut se demander si ce

n’est pas une évolution analogue, mais toutefois différente (et «plus poussée»)

qui a conduit au «cormus» des plus primitives de celles-ci.

En résumé, du Drapamaldiopsis aux Chara, s’observe une évolution du type

cladomien conduisant des cladomes a pleuridies aux cladomes à phyllidies,

puis à un type évolué de ceux-ci. Et cette évolution montre que les phyllidies

260

M. CHADEFAUD

Fig. 6. - Chara (fin). - A - Cladome primaire du thalle, prétendu protonémien. Segment 1

très court avec rhizoïdes sur le sous-segment nodal. Segment 2 très long, également avec

verticille de (Si, sur le sous-segment nodal. Segments suivants (3-4...) imparfaits, (cf. A

o,’ f' 4 l Fas d ’ axes rec ouvrants. Premier cladome normal (cl) dans l’aisselle d’un des

a< î Segr "f nt coxa * d’un ax e phyllidien (3 1 donnant naissance à l’axe caulidien Ci x

c'Mome-fik axillaire. Dans le sous-segment internodal (in) de ce segment des

cloisons ont del,mite le segment coxal de a x. Du segment nodal (n) sont nés des axes

C °-l ^ 2 C * sche J ma) ' ~ C . Disposition des organes reproducteurs (schéma) : organe

male (M) au sommet d un axe (3 2 (homologue aux (3 2 p) ; organe femelle (F) au sommet

d un axe (3 3 (homologue aux (3 3 C). - D - Organe femelle (schéma). Sur le sous-segment

noda de son segment coxal (avec centrale en noir), verticille de cinq axes involucraux

(P 4i) enveloppant 1 oocyste (oo), autour duquel ils sont en réalité torsadés.

ne sont pas des pleuridies évoluées, et qu'elles ne sont pas forcément portées

par des axes a structure sympodiale. Elles peuvent toutefois remplacer les

pleuridies des cladomes primitifs.

B. - CÉRAMIALES

Ce que nous apprennent ainsi les Charales peut être mis en parallèle avec ce

que montrent les Céramiales (cependant sans parenté avec les Charales) parmi

lesquelles on trouve :

a) Des espèces formées de cladomes à pleuridies. Ex.:

le Halurus equisetifolius (dont les cladomes rappellent ceux des Batrachosper-

CHARALES ET CÉRAMIALES

261

mum et des Dudresnaya) ;

- le Crouania attenuata, avec sur chaque segment un verticille de quatre pleu-

ridies;

le Wrangelia penicillata, dont les verticilles de pleuridies comportent: une

pleuridie primaire, indiquant une bilatéralité (cf. Nitella et Chara) et dont les

segments se séparent de l’initiale apicale par un cloisonnement oblique (cf.

Rhodomélacées; v. plus loin). De cette obliquité dépend la position de la pleuri¬

die primaire; de plus, elle varie de chaque segment au suivant selon un mode

scorpioïde (= en zig-zag) de sorte que la disposition des pleuridies primaires

est elle aussi scorpioïde (fig. 7).

Cette espèce montre ainsi que les cladomes à pleuridies peuvent subir une

importante évolution progressive, sans pour autant devenir des cladomes à

phyllidies.

Fig. 7. - Wrangelia penicillata : ordre «phyllotaxique» des pleuridies. - A - Très jeune

cladome: disposition «scorpioïde» (en zig-zag) des pleuridies I (a, axe cladomien;noter

sa dorsiventralité; 7T 1, pleuridies 1, insérées sur le dos de l’axe, alternativement à droite

et à gauche de sa ligne médiane; autres pleuridies encore non développées). - B Dia¬

gramme de trois verticilles pleuridiens successifs. Dans chaque verticille, cinq pleuridies

(1.2.3.4.5.) en ordre approximativement quinconcial (div. 2/5). Dans les verticilles

successifs, disposition scorpioïde de la pleuridie I (cf. A), et ordre quinconcial, alterna¬

tivement dextre et sénestre (v, côté ventral).

b) Des espèces au contraire formées de cladomes à phyllidies. Exemples :

- l’ Antithamnion cruciatum (fig. 8, A), avec: segments de l’axe caulidien (a)

non subdivisés en deux sous-segments; sur chacun d’eux, près de son sommet,

un cycle de quatre phyllidies (<p), dont deux majeures, en croix avec deux

mineures (qui peuvent manquer) ; des phyllidies formées d’axes P 1 porteurs

de P 2; à la base de chaque phyllidie, un segment coxal (cf. Chara); les organes

reproducteurs sont sur les (3 1, sur lesquels les tétrasporocystes remplacent

chacun un P 2 (cf. Chara, dont les organes mâles terminent des P 2, et les organes

262

M. CHADEFAUD

femelles des 0 3).

F lg . 8. - Ceramiales: cladomes à phyllidies. - A - Antithamnion cruciatum. En principe

quatre phyllidies \Ç par segment de l’axe caulidien CX : deux majeures (t/?l) et deux mi¬

neures (0 2) qui peuvent manquer. 01 et 0 2, axes phyllidiens. - B - Callithamnion

audresnayi ( = purpurascens Harvey): une seule phyllidie (<p _ la première des y 1) par

segment de a. - B’ - Idem : segment fertile d’un axe a d’un thalle femelle : en plus de

la phyllidie deux coxales (c) de phyllidies mineures (?) ou de pleuridies (?). On sait

que 1 une d’elles porte un filament carpogonial et que toutes deux se divisent pour don¬

ner une cellule auxiliaire.

Une telle structure est tout à fait comparable à celle des cladomes à phylli-

ies “ es Charales, sauf toutefois que les segments caulidiens ne se subdivisent

pas en deux sous-segments. Comme dans le cas des Charales, elle doit résulter

de révolution d’un type à pleuridies, comportant la disparition de celles-ci.

On doit en effet remarquer que, d’une façon générale, sur les cladomes à pleu-

ridies de certaines espèces, les cladomes-fils remplacent chacun une pleuridie.

Dans les cladomes à phyllidies de VA. cruciatum, toutes les pleuridies seraient

ainsi remplacées par des cladomes-fils, mais ceux-ci réduits à des phyllidies ( =

brachyblastes) formées de brachy-cladomes 0. On retrouve ainsi l’idée selon

aquelle (cf. Charales) les phyllidies ne sont, ni des pleuridies évoluées, ni forcé¬

ment subordonnées à un axe a sympodial.

- les Callithamnion, tels que le C. dudresnayi Crouan (= purpurascens Harvey)

lg i'.j. B ' 1 S nC dlffèrent de l' A - cruciatum que parce que chaque segment

caulidien ne porte plus qu’une seule phyllidie : la majeure I.

Toutefois, sur les segments fertiles femelles il y a encore deux coxales qui,

““ P lus bas d ue ia phyllidie, ne sont peut-être pas les coxales de

phyllidies mineures, homologues à celles de YAntithamnion ; elles peuvent

et L re 11 ., s coxales de pleuridies (non développées), non remplacées par des

phyllidies, donc etre pleundiennes, non phyllidiennes (?) (V. plus loin: Rhodo-

melacees, fig. 10 et 11).

CHARALES ET CÉRAM1ALES

263

La réduction du nombre des phyllidies à un seul par segment caulidien

est le résultat d’une bilatéralité analogue à celle des segments du Wrangelia ,

mais plus accusée. D’autre part, l’ordre «phyllotaxique» est hélicoïdal distique

et non scorpioïde.

c) Des espèces également à phyllidies, mais évoluées, à la façon des Chara ,

bien que ce soit autrement, et d’ailleurs diversement. Exemples :

- L ’Antithamnion plumula (fig. 9 A), dont l’évolution s’est manifestée par

une tagmatisation des cladomes à phyllidies (cf. CHADEFAUD, 1954).

Fig. 9. - Céramiales à cladomes tagmatisés. - A Antithamnion plumula. Tagme de 5

segments portant chacun 4 phyllidies ç? (deux majeures, en croix avec 2 mineures; cf.

A. cruciatum, mais mineures beaucoup plus réduites); sur le dernier segment, l’une des

ip est développée en une d>; bilatéralité: grandes $ majeures toutes à gauche; d’un tagme

au suivant, inversion de la bipolarité: par suite, d>alternativement à droite et à gauche.

Cette inversion traduit un ordre hélicoïdal distique des tagmes. — B - Heterosiphonia

plumosa. Deux tagmes, l’un de 2, l’autre de 3 segments. Même disposition que chez IM.

plumula, mais axe caulidien, axes phyllidiens 0 1 et partie inférieure de certains des

(3 2 revêtus de péricentrales (cf. fig. 10 A).

Comme chez VA. cruciatum, chaque segment caulidien porte quatre phylli¬

dies, dont deux majeures, 1 et II, et deux mineures rudimentaires en croix avec

les précédentes; chaque phyllidie majeure = 1 0j + des 02 et des $ 3 . Mais l’axe

caulidien est formé de tagmes successifs, comportant tous le même nombre de

segments. Ces tagmes ont une bilatéralité telle que, sur chacun d’eux, les phylli¬

dies majeures I sont toutes du même côté. Cette bilatéralité s’inverse, de chaque

tagme au suivant, selon un ordre hélicoïdal distique (cf. Callithamnion).

264

M. CHADEFAUD

Les tagmes successifs sont séparés par des cloisons obliques (cf. Wrangelia

et, plus loin, Rhodomélacées). Au sommet de chaque tagme, la dernière phyllidie

majeure I, ou phyllidie <£ se développe en un cladome-fils : cela illustre que les

phyllidies sont des brachyblastes, et non des pleuridies évoluées.

Cette structure traduit un rythme dans le développement de l’axe caulidien

(a), donc dans le fonctionnement de sa cellule initiale apicale. Selon un rythme

défini, celle-ci se cloisonne d’abord plusieurs fois transversalement, pour donner

les segments normaux de cet axe, puis obliquement, pour donner son dernier

segment, celui qui porte la phyllidie 4>. On remarquera que sans les cloisons

transversales on retrouverait le cas des Callithamnion , chez lesquels un tel

rythme n’existe pas (à moins qu’il ait été supprimé?).

- Les Rhodomélacées, parmi lesquelles nous examinerons seulement les Poly-

sivhonia, les Heterosiphonia et les Pterosiphonia.

On retrouve chez ces Algues une tagmatisation analogue à celle de VAnti-

thamnion plumula, mais avec des axes caulidiens (a) et parfois aussi les axes

phyllidiens (/?), formés de cellules dites «centrales», entourées de cellules «péri-

centrales», qui sont les coxales de pleuridies. Quand celles-ci sont développées,

ce qui n’est pas toujours le cas, leur ensemble forme un cortex pleuridien.

En ce qui concerne les segments caulidiens, cela donne ce qu’on observe notam¬

ment chez les Polysiphonia , chez lesquels chacun des segments de l’axe O porte

latéralement, près de son sommet, une phyllidie (réduite à un trichoblaste

incolore et caduc), et plus bas un cycle de coxales pleuridiennes ou péricentrales,

qu entoure un cortex pleuridien chez certaines des espèces, mais non chez

toutes (fig. 10 A).

Fig. 10. - G. Polysiphonia : structure et disposition des segments de l’axe caulidien des

cladomes. - A - Un segment: cellule axiale Oc (= centrale); tout autour, verticille de

pleuridies, avec coxales ex (= péricentrales) et cortex pleuridien c77; près du sommet,

coxale ex <P d’une phyllidie $ (= réduite à un trichoblaste). Pour une interprétation

possible de cette coxak, v. fig. 12. — B - Disposition hélicoïdale des segments successifs,

indiquée par celle des «P. Péricentrales seules figurées; espèces à 4 péricentrales par

segment caulidien ; par suite, entre les $ successives, div. = 1 / 4 .

CHARALES ET CÉRAMIALES

265

Cette structure, qu’on doit qualifier de «rhodoméloïde», peut être inter¬

prétée, quant à son origine phylogénétique, en prenant comme point de départ:

1 . le Wrangelia penicillata (fig. 7) dont chaque segment caulidien porte, près

de son sommet, un verticille de pleuridies disposées (approximativement) en

ordre quinconcial, et dont la première seule peut porter, sur sa base, un cladome-

fjls; 2. les Callithamnion (fig. 8 B), dont chaque segment caulidien porte, près

de son sommet, une phyllidie unique (qui peut se développer en un cladome-fils)

et plus bas une paire de coxales, peut-être pleuridiennes (présentes seulement

sur les segments fertiles des thalles femelles).

On se trouve là en présence de deux variantes de la structure fondamentale

représentée par le diagramme A de la fig. 11, comportant une pleuridie dorsale

a, une pleuridie ventrale b, et des pleuridies latérales en ordre scorpioïde (en

zig-zag). Chez le Wrangelia, du fait d’une dorsiventralité accusée et de la bilaté¬

ralité des axes caulidiens, les pleuridies a et b ont été déplacées, alternativement

vers la gauche ou vers la droite, l’une des pleuridies latérales proches de b a été

Fig. Il - G. Polysiphonia : origine possible de l’organisation des segments caulidiens (dia¬

grammes schématiques). - A - Segment caulidien primitif (théorique): seulement un

verticille de pleuridies, mais bilatéralité nette. Pleuridies a (= 1), dorsale, et b (= 2),

ventrale, dans le plan de symétrie; pleuridies suivantes (3,4,5,6) en ordre scorpioïde

(en zig-zag). - B - Wrangelia penicillata (cf. fig. 7) : a et b déportées vers l’un des côtés

(ici, côté gauche); pleuridie 6 supprimée;en conséquence, pleuridies en ordre quinconcial

et plan de symétrie oblique. - C - Callithamnion (cf. fig. 8) : verticille dédoublé; verti¬

cille supérieur portant seulement la pleuridie a (remplacée par la phyllidie i/>; b sup¬

primé ("h); verticille inférieur avec seulement les pleuridies 3 et 4, présentes seulement

sur les segments femelles fertiles, et réduites à leurs coxales. - D - Polysiphonia : espèce

à quatre péricentrales par segment (cf. fig. 10): verticille également dédoublé; verticille

supérieur ne portant également que a (= phyllidie <p) ; mais verticille inférieur portant

encore les pleuridies 3,4,5 et 6 du Wrangelia, en ordre scorpioïde. Chez d’autres espèces,

ces pleuridies sont plus nombreuses; il y a alors un nombre plus elevé de pericentrales

par segment.

266

M. CHADEFAUD

supprimée, et il en est résulté une disposition quinconciale, avec axe géomé¬

trique oblique (diagr. B) (1). Chez les Callithamnion n’ont été conservés que la

pleuridie dorsale a, remplacée, par une phyllidie, et (sur les segments femelles

fertiles) l’un des couples des pleuridies latérales (réduites à leur coxale). De la

sorte, le verticille pleuridien de A a été dédoublé en un verticille phyllidien et

un verticille demeuré pleuridien, celui-ci situé plus bas sur les flancs de la cellule

axiale (diagr. C). En combinant ces deux évolutions, on arrive au diagr. D, com¬

portant un verticille de deux phyllidies, dont la ventrale peut manquer, et plus

bas un verticille de pleuridies latérales, dont le nombre peut d’ailleurs être

supérieur a quatre : c’est la précisément le diagramme des segments caulidiens

«rhodoméloïdes»: tels que ceux des Polysiphonia (fig. 10 A).

Le dédoublement du verticille pleuridien du diagramme A en un verticille

phyllidien superposé à un verticille demeuré pleuridien n’est pas sans rappeler

la subdivision des segments des Charales en un sous-segment nodal porteur

de phyllidies, et un sous-segment internodal. Mais celui-ci ne porte pas de pleu¬

ridies, et d’autre part il n’y a pas, chez les Rhodomélacées, de cloison transver¬

sale entre les deux verticilles, à moins toutefois qu’on admette que, dans la

cellule axiale des Polysiphonia, la petite cellule portant la phyllidie est l’équi¬

valent très réduit, du sous-segment nodal des Charales (fig. 12) (?).

Fig. 12 - Polysiphonia : comparaison possible avec les Charales. - A - Schéma d’un segment

caulidien de Charale, avec sous-segments internodal in et nodal n, celui-ci porteur d’un

verticille de phyllidie <p. Pas de pleuridies. - B - Schéma d’un -id- de Polysiphonia :

sous-segment nodal réduit à la coxale d’une phyllidie unique (= trichoblaste) ; sous-

segment internodal entouré de coxales pleuridiennes ex (= péricentrales).

(1) Cette transformation d’un diagramme hexagonal, de 2 + 4 pièces, en un diagramme

pentagonal quinconcial est exactement celle qui a donné le calice pentamère quinconcial

de la plupart des Dicotylédones. Il y a là un remarquable exemple de parallélisme entre

des groupes extrêmement éloignés et, si l’on veut, un argument en faveur des théories

structuralistes (cf. CHADEFAUD, C. R. Ac. Sc., Paris 1955 240: 1129-1131

CHARALES ET CÉRAMIALES

267

Cela dit, la tagmatisation des axes caulidiens ou phyllidiens des Rhodomé-

lacées est indiquée par la présence sur le segment terminal de chaque tagme,

d’une phyllidie 4>, parfois deux, distincte des autres parce qu’elle peut porter

un cladome-fils, ou être remplacée par un tel cladome. De la sorte :

1. L’Heterosiphonia plumosa (fig. 9, B) est directement comparable à VA.

plumula (fig. 9, A), avec tagmes caulidiens porteurs de deux rangées de phylli-

dies, rectilignes et opposées, et sur leur dernier segment une phyllidie dont

la position indique que de chaque tagme au suivant il y a inversion de la bilaté¬

ralité, donc que les tagmes successifs sont en ordre hélicoïdal distique. Mais

ces tagmes ne sont que de deux ou trois segments, et ceux-ci sont revêtus de^

péricentrales (= coxales pleuridiennes). Dans les phyllidies $ l’axe 3 1 est formé

de tagmes à deux segments, également revêtus de péricentrales; les axes (3 2

débutent par un tagme à deux segments, parfois pareillement revêtus; le reste

n’est pas tagmatisé; les 3 3 ne le sont pas non plus.

2. Une organisation semblable se retrouve chez les Pterosiphonia , par ex.

le P. parasitica (fig. 13, A), sauf qu’ils n’ont pas de phyllidies <p, et que leurs

phyllidies $ sont entièrement revêtues de péricentrales. Les tagmes caulidiens

sont de deux segments; les (3 1 sont formés d’un tagme plurisegmenté, suivi

de tagmes à deux segments ; les 3 2 ne sont pas tagmatisés. Chez le P. complanata

les (3 2 portent des (3 3. Chez le P. pennata, au contraire, il n’y a pas de 0 2.

Dans tous les cas, les axes (3 sont disposés en séries rectilignes opposées, comme

chez VA. plumula et VH. plumosa, et les tagmes successifs sont en ordre distique.

On peut penser que par rapport à VAntithamnion, les Pterosiphonia sont

plus évolués, leur évolution s’étant traduite par la suppression des phyllidies

y; et par la formation d’un revêtement complet de péricentrales sur les (3- .Cela

est d’ailleurs justifié par la comparaison avec les Brongniartella et Boergeseniella,

car :

- Chez le Brongniartella byssoides (fig. 13, B) les < p n’ont pas encore disparu,

mais dans les $ (= brachyblastes) on observe un revêtement de péricentrales

sur l’axe P 1 et sur la partie basale de certains des P 2. Le sommet de ceux-ci,

et les autres P 2, au contraire encore dépourvus de péricentrales, sont des tricho-

blastes (pigmentés et non caducs);

- chez le Boergeseniella fruticulosa (fig. 13, C), dont la tagmatisation est

très régulière, l’organisation est presque celle des Pterosiphonia, sauf qu’existent

encore des phyllidies <p (= trichoblastes), et que leur $ et * sont en ordre héli¬

coïdal non distique.

3. Les Polysiphonia (fig. 10, 13B, 14 et 15) diffèrent au contraire davantage

de VH. plumosa, et leurs caractères semblent indiquer une évolution différente:

leurs phyllidies <E> et \p sont en effet disposées, non pas en ordre distique, mais

en ordre hélicoïdal polystique, avec divergence variable selon les espèces. De

plus, on trouve, chez certains d’entre eux une disposition aberrante des phylli¬

dies < î ) , et chez toutes les espèces les ip sont réduites à des trichoblastes, incolores

et caducs.

La tagmatisation indiquée par les $ est plus ou moins irrégulière, le nombre

des segments variant d’un tagme à l’autre. Ainsi, le long de l’axe caulidien,

268

M. CHADEFAUD

Fig. 13. - Pterosiphonia : Phyllidie $ (= brachyblaste) du P. parasitica, comparée à celles

du Brongniartelk byssoïdes et du Boergenseniella fruticulosa (v. le texte). - A - Ptero¬

siphonia : axe caulidien a et axes phyllidiens 0 1 et 0 2 entièrement revêtus de péricen-

trales; tagmatisation régulière de Ot, avec tagmes de 2 segments; premier tagme de 0 1 à 5

segments, les suivants à deux; 02 non tagmatisés (ou peut-être réduits à leur premier

tagme plunsegmenté) ; pas de trichoblastes. - B - Brongniartelk : axes a et fil également

revetus de péricentrales, mais ne l’est que seulement la base de certains des (î 2 ; tagmati¬

sation moins régulière, les tagmes étant de un ou deux segments;encore des phyllidies i p,

et des trichoblastes, formés par ces <p, et par le sommet ou la totalité des 0 2. — C -

Boergeseniella : axes a et (3 1 des phyllidies entièrement revêtus de péricentrales, ainsi que

certmns des (3 2 phyllidiens, mais encore des trichoblastes sur Oi (= des y?) et sur les (3

des q*;tagmatisation très régulière (tagmes caulidiens à 2 segments): ordre hélicoïdal

régulier des tp et <l>sur les axes caulidiens. En Cl, 0 1 (avec sommet S), (3 2 normaux et

P 2 réduits a des trichoblastes d’une phyllidie <î>.

CHARALES ET CÉRAMIALES

269

a varie de 3 à 13 chez le P. furcellata (fig. 14, A) et de 5 à 7 chez le P. urceolata.

Mais chez le P. nigrescens , il est constamment de 2 ou 3 (et de 2 chez le Borge-

seniella fruticulosa : fig. 13, C).

Sur chaque tagme, les phyllidies sont disposées sur une hélice dextre, et

l'hélice de chaque tagme continue celle du précédent. D’un tagme a l’autre on ne

retrouve donc pas l'inversion observée chez VA. plumula, VHeteros.phoma et les

Pterosiphonia. La phyllidie du dernier segment est une phyllidie * portant

sur sa cellule coxale, et à sa gauche, un dadome-ffls. Peut-etre faudra^t-ilplutot

penser qu’elle est représentée par ce cladome-fils, avec une phyllidie 4> (- tricho¬

blaste) sur sa cellule coxale, et à sa droite. Chez certaines espèces, une partie

des segments sont dépourvus de phyllidies </> : amsi-ll n’j en a pas du tout chez

le P. lanosa f= fastigiata) , ce qui peut être le résultat d’une évolution régressive.

Entre les phyllidies des segments successifs, la divergence varie selon les

espèces. Elle dépend du nombre de péricentrales par segment. Quand ce nombre

est 4, la div. = 1/4 (fig. 10, B).

Chez certaines espèces, cette organisation est perturbée par l’intercalation

entre les tagmes successifs, d’inter-tagmes non hélicoïdaux. Nous l’avons déjà

signalé autrefois (CHADEFAUD, 1967). En fait, chaque inter-tagme constitue

la base du tagme suivant et de la sorte chaque axe caulidien a pour base un inter-

tagme plus ou moins long, dépourvu de phyllidies. Ont des axes caulidiens

à inter-tagmes, par ex. :

- Le Polysiphonia sertularioïdes. Sur l’axe représenté par la fig. 14 C les

tagmes hélicoïdaux sont de deux segments portant, le premier une phyllidie

(= trichoblaste), le second une phyllidie 4> (= trichoblaste + cladome-fils).

L’hélice de chaque tagme continue celle du précédent. Les inter-tagmes sont de

trois ou quatre segments. Mais on observe aussi des axes à structure differente.

- Le P. tenerrina. Ses tagmes hélicoïdaux ont un nombre variable de seg¬

ments, et là encore il y a continuité de leurs hélices. Us ne portent generalement

que des phyllidies Entre eux, les inter-tagmes ont de un a trois segments,

dont l’un porte généralement une phyllidie 4>, représentée par un cladome-hls.

D’après les dispositions de cette phyllidie et des phyllidies f, on peut penser

que fondamentalement les inter-tagmes étaient de trois segments a disposition

orthomère, avec deux rangées rectilignes et opposées de phyllidies, donc avec

une organisation semblable à celle des tagmes de VA. plumula (cf. fig. 9, A).

Mais une seule des phyllidies se développe (une 4>), qui peut meme manquer;

les autres demeurent virtuelles. Les fig. 15, B, C, D, montrent certains des cas

réellement observés: inter-tagmes réduits à deux segments, P“ s * un seul ’

disposition variable de l’unique phyllidie $, et absence des autres phyllidies.

Si le schéma A est valable, il peut indiquer qu’ancestralement les Polysiphoma

ont eu l’organisation et la tagmatisation de VA. plumula , de YHeteros.phonu,

plumosa, par rapport auxquels ils seraient d’un type plus évolue, leur évolution

ayant réduit un sur deux des tagmes orthomères à des mter-tagmes, qui ensuite

ont généralement disparu, tandis que les autres devenaient helicomeres.

270

M. CHADEFAUD

Source : MNHN, Paris

CHARALES ET CÉRAM1ALES

271

Fie 14 - Polysiphonia : cladomes; tagmatisation indiquée par les 'ï* ou par les cladomes-

*«, - A - P. fnrcellaia : tagmatisation très irrégulière ; tagmes de 13 11, 5 et 8 segments.

Mais cette irrégularité tient peut-être à la présence d'intertagmes (!) cf. C. - B - r

thuyoïdes : tagmatisation presque régulière; tagmes de 2 ou 4 segments (rarement davan¬

tage) - C P. sertularioïdes (= macrocarpa Harvey) ; alternance de tagmes (en blanc) et

d'intertagmes (pointillés). Tagmes a, b, c de deux segments portant le premier une sf

(= trichoblastes). le second une 4> (= trichoblaste + ébauché de cladome-ffls; pour b

celui-ci n’est pas visible) ; qJ et 4>en ordre hélicoïdal, avec divergence - 1/4. Segments

des tagmes numérotés de 1 à 6.

Fie 15 - Polysiphonia tenenima ; intertagmes. - A - Structure fondamentale probable (!)

"des intertagmes; 3 segments en ordre rectiligne (orthomerle) avec deux rangs opposes

l'un de phyllidies <î>(a, b, c), l'autre de phyllidies gl (a', b’ c’,). Sur les tagmes seulement

des m en ordre hélicoïdal, avec div.; 1/4. La ptesence des Intertagmes _n altéré pas cet

ordre et cette divergence. De tels intertagmes ont ete reeUement observes mais sans n

m _ B à D - Intertagmes observés, portant seulement l'une des <P (a ou b), et réduits a 2

segments ou un seul. Dans quelques cas, les deux rangées de phyllidies des intertagmes

réelles ou virtuelles) étaient en quadrature, et non opposées.

C. - CONCLUSION

En définitive, il résulte de l’étude comparative des Charales et des Ceramiales

que malgré des différences qu’on ne saurait négliger, on retrouve dans ces deux

groupes une structure cladomienne évoluant selon le même schéma, de sorte

qu’on y trouve, d’abord des cladomes à pleuridies, ensuite des cladomes a

phyllidies d’un type encore simple, enfin des cladomes a phyllidies d un type

évolué, plus ou moins complexe et sophistiqué.

Charales et Céramiales n’étant nullement apparentées, cela signifie que le

type cladomien et son évolution ont pu apparaître, d’une manière polyphyle-

tique, indépendamment dans les divers phylums d’Algues, et que par conséquent

ils résultent d’une tendance évolutive commune à la plupart d’entre eux, sinon a

tous. Dès leur origine, cette tendance devait être inscrite dans leur genome,

comme si elle avait, dans le super-embranchement des Algues, un caractère

fondamental. Mais ensuite elle ne s’est manifestée qu’à partir d’un certain niveau

de l’évolution, qui n’a été atteint qu’en fonction d’autres tendances génoty¬

piques, et sans doute aussi contrôlé par l’action du milieu.

Toutefois, on doit remarquer que la structure cladomienne n’a pas été egale¬

ment réalisée dans tous les groupes d’Algues ; elle l’a été très bien chez les

Floridées et diverses Phéophycées, mais beaucoup moins chez les Chlorophycees,

ou seules les Charales (et à un moindre degré les Draparmldta) sont franchement

cladomiennes; dans les autres groupes il n’y a presque pas d’espèces cladomien-

nes; encore ne le sont-elles pas parfaitement, ou même il n’y en a pas du tout (1).

(1) Pourtant, il y en a déjà chez les Cyanophycées: cladomes (à la vérité imparfaits) du

Stigonema mamilbsum, par ex.

272

M. CHADEFAUD

On remarquera ici que les groupes dans lesquels la tendance cladomienne ne

s’est que rarement manifestée, ou fait défaut, sont par contre ceux dans lesquels

abondent les espèces monadoïdes : Volvocales, Euglénomonadines, Crypto-

monadines, Chrysomonadines, etc., tandis qu’au contraire il n’y a chez les Flo-

ridées et les Phéophycées, si souvent cladomiennes, aucune espèce flagellée

nageuse. Ainsi, Floridées et Phéophycées ont manifesté des tendances essen¬

tiellement «végétales», tandis que dans les autres groupes on observe une ten¬

dance «animale» accusée. Autrement dit, de par leur génome initial, certains

phylums sont purement végétaux, tandis que les autres conduisent au Règne

animal.

A propos des Charales, on a vu que la rareté, chez les Chlorophycées, des

formes cladomiennes, peut tenir en partie à une autre cause : chez celles qui

ont atteint le stade cladomien, celui-ci a pu être dépassé, de sorte qu’au lieu

d’un thalle cladomien elles ont un cormus, en principe feuille. Selon P1CKETT

HEAPS et MARCHANT (1972), puis CHADEFAUD (1977), cela concerne les

Chlorophycées «à phragmoplastes», dont les plus évoluées sont les Charales,

et dont les formes surévoluées à cormus, seraient les Cormophytes (= Arché-

goniates).

Enfin, la notion de surévolution des cladomes, ainsi envisagée, conduit à

remarquer que, sans quitter les Algues, on trouve aussi des espèces métaclado-

miennes, dont le thalle est formé de cladomes surévolués, sans pour autant

etre devenu un cormus. La surévolution en jeu peut se concevoir par compa¬

raison avec ce que montrent les Gracilaria (selon BODARD et KLING, 1978):

le s ° mmet de leurs cladomes est typiquement cladomien, avec filament axial

hehcomère et cortex pleuridien, mais dans leur partie plus âgée la structure

cladomienne s’efface, du fait que les cellules axiales et celles de la partie interne

du cortex pleuridien forment un pseudo-parenchyme médullaire. Cette partie

du thalle devient ainsi méta-cladomienne, et il est possible que ce soit aussi

le cas des autres Floridées à rameaux composés d’une moelle et d’un cortex.

Mais d’autres Algues n’ont pas une structure cladomienne reconnaissable sans

doute pour une autre raison : elles auraient évolué sans passer par un stade

cladomien typique, et seraient donc para-cladomiennes. Tels sont peut-être

les Fucales, les Dictyotales, les Laminariales (?).

(manuscrit accepté le 15 mai 1979)

AUTEURS CITÉS

ARDRÉ, F., 1967 a - Remarques sur la structure des Pterosiphonia. Rev. algol. 1: 37-77.

ARDRÉ, F., 1967 b - Nouvelles remarques sur la structure des Pterosiphonia et leurs

rapports systématiques avec les Polysiphonia. C. R. Acad. Sc. Paris, D 264: 2192-2195.

BC> 7^73 ) ’ M Ct KLING ’ R '’ 1979 ~ Gracila ria verrucosa : un cladome? Rev. algol. 14:

CH 7T87 AUD ’ M ’’ 1954 ~~ SUr ^ mor P hoIo S ie de quelques Céramiacées. Rev. algol. 1:

CHARALES ET CÉRAMIALES

273

CHADEFAUD, M., 1955 — Sur la pentamérie des dicycles floraux. C. R. Acad. Sc. Paris

240: 1129-1131.

PHADEFAUD M 1960 — Les végétaux non vasculaires (Cryptogamie). T.I. du Traité

de Botanique systématique de M. CHADEFAUD et L. EMBERGER, XV + 1018 p„

Masson, Paris.

CHADEFAUD, M., 1967 — Remarques sur la tagmatisation et la phyllotaxie des Floridées

Rhodomélacées. C. R. Ac. Sc. Paris, 264: 2888-2890.

CHADEFAUD, M., 19676 - Les Algues, de leur origine à celle des Plantes supérieures.

Ann. sci. de l’Université de Reims et de l’ARERS, 14: 37-48.

CHADEFAUD, M., 1977 - Sur l’évolution des zoïdes Chlorophycées et l’origine algale

des Cormophytes. C. R. Ac. Sc. Paris 284: 227-229.

CHADEFAUD, M., 1979 - Ontogénèse et morphogénèse des Algues : colloque de Banyuls

sept. 1978; exposé préliminaire. Rev. algol. 14: 66-67.

DUCREUX, G., 1975 - Corrélations et morphogénèse chez Chara vulgans, cultive in vitro.

Rev. gén. Botanique 82: 215-357.

GINSBURG-ARDRÉ, F. et CHADEFAUD, M., 1964 - Remarques et précisions sur la

structure des Floridées rhodoméloïdes. C. R. Ac. Sc. Paris 259: 1421-1431.

GINSBURG-ARDRÉ, F., 1966 - La tagmatisation, l’a pseudo-dichotomie, la structure

pseudo-sympodiale et les brachyblastes chez les Ceramium. C. R. Ac. Sc. Pans 262:

1216-1219.

L’HARDY-HALOS, M.T., 1966 — Sur le développement expérimental des pleuridies chez

quelques Antithamnion. C. R. Ac. Sc. Paris 263: 242-245.

L’HARDY-HALOS, M.T., 1966 - Recherches sur la morphologie des Céramiales : la notion

de brachycladomes. C. R. Ac. Sc. Paris 262: 64-67.

L’HARDY-HALOS, M.T., 1970 — Recherches sur les Céramiacées et leur morphogénèse.

I. Rev. gén. Bot ’. 77: 211-287.

L’HARDY HALOS M T 1975 - A propos des corrélations morphogènes contrôlant

l'initiation des ramifications latérales chez les Algues à structure cladomienne typique.

Bull. Soc. phycol. France 20: 1-6.

PICKETT-HEAPS, J.D. et MARCHANT, H.J., 1972 - The phylogeny of green Algae:

a new proposai. Cytobios. 6: 255-264.

SUNDARALINGAM, V.S., 1954 - The developmental morphology of Chara zeylantca

Willd. J. Indian Bot. 33: 272-297.

SUNDARALINGAM, V.S., 1960 - Comparative morphology of the Charophyta. Proc, of

the Symposium ofAlgology, New Dehli, India : 78-84.

Source : MNHN, Paris

275

OUVRAGES REÇUS POUR ANALYSE

P. BOURRELLY, M. RICARD

BERTHOLD, W.H., 1978'- Ultrastrukturanalyse der endoplasmatischen Algen

von Amphistegina lessonii d’Orbigny, Foraminifera (Protozoa) und ihre

systematische Stellung. Arch. Protistenk., 120: 16-62.

L’auteur observe des algues unicellulaires dans le cytoplasme d’un foramini-

fère des îles Hawaï.

L’étude en microscopie électronique permet, d’après le mode de division

nucléaire, de penser qu’il s’agit de diatomées. Ces diatomées conservent leurs

caractères cytologiques mais la carapace siliceuse est fragmentée et très réduite.

Les symbiotes connus chez les foraminifères sont le plus souvent des Dinophy-

cées, plus rarement des Chlorophycées et des Cryptophycées. Jusqu’au mémoire

de BERTHOLD, un seul cas de symbiose de foraminifère et diatomées avait été

observé par DIEZ-ELBRÂCHTER (1971).

Le travail de BERTHOLD est étayé par une illustration très démonstrative

de 45 photographies d’ultrastructure en microscopie électronique.

FINDLAY, D.L. and KL1NG, H.J., 1978 A species list and pictorial reference

to the phytoplankton of central and northern Canada. Fisheries and Marine

Service, Manuscript Rep. 1503, part I: 619p.; part II: 619 p.

Ces deux ouvrages constituent un ouvrage pratique destiné à aider les cher¬

cheurs appelés à travailler sur les lacs du centre et du nord canadien dans des

domaines touchant à l’algologie. ,

615 taxons sont regroupés, appartenant aux Cyanophycées, Euglénophycees,

Chlorophycées, Chrysophycées, Diatomophycées et Dinophycées. Chaque

espèce fait l’objet d’une fiche indiquant sa taille, les lieux et périodes de récolte

et une figure reprise sur des ouvrages d’auteurs spécialisés: HUBER-PESTA-

LOZZ1, SKUJA, SMITH, UHERKOVICH, HUSTEDT, etc. En dehors de quel¬

ques Desmidiées au dessin trop sommaire, les illustrations sont, dans l’ensemble,

bien choisies, suffisamment claires et détaillées. Le nom de l’auteur des figures,

souvent différent de celui de l’éditeur qui a effectué la révision globale d’un

groupe, n’est pas mentionné.

Une mise à jour, à l’aide des travaux d’algologie récents, serait utile pour

supprimer quelques lacunes ou inexactitudes : certains noms d'espèces, sont

encore orthographiés avec une majuscule; Marssoniella elegans est signalé par-

source . MNHN, Paris

276

OUVRAGES REÇUS POUR ANALYSE

mi les Cyanophycées alors que les observations de KOMAREK & VAVRA

(1967) ont démontré qu’il s’agit d’un groupement de spores d’une microspo-

ndie parasite des ovocytes de Cyclops ; quelques Xanthophycées sont signalées

parmi les Chrysophycées et une bactérie est répertoriée dans les Pyrrophytes;

la classification des Desmidiées serait à revoir. Enfin, il n’est pas fait état du

troisième tome de l’ouvrage de base de P. BOURRELLY (1970) sur les Algues

d’eau douce.

L’index complet placé à la fin de chacun des deux volumes facilite l’emploi

e cette liste illustrée, indispensable à tous ceux qui s’intéressent au phytoplanc-

ton lacustre de ces régions du Canada.

GRANHALL, U., ed., 1978 - Environmental rôle of Nitrogen fixing Blue-

green Algae and asymbiotic Bacteria. Ecological Bulletins, N.F.R. Stockholm

26: 1-391, 100 Sw. Cr., broché.

Ce volume est le compte-rendu d’un symposium tenu à Uppsala en 1976

Les algologues seront intéressés par les deux premiers chapitres se rapportant

au rôle des Cyanophycées aquatiques et subaériennes. Il s’agit de communica¬

tions originales. Citons simplement G.E. FOGG : Nitrogen fixation in the Océan-

R.H. BURRIS & R B. PETERSON: Nitrogen-fixing blue-green algae. their

H 2 metabolism and their actrnty in freshwater lakes; J.R. GALLON ■ Calcium

and nitrogen fixation by Gloeocapsa-, P.A. REYNAUD & P.A. ROGER: N,

îxing algal biomass in Sénégal rice fields; J.K. JONES & R.E. WILSON: the

fate of nitrogen fixed by a free-living blue-green alga; J. SKUJINS & B. KLU-

BEK: Nitrogen fixation and cycling by blue-green algae- lichen- crusts in arid

rangeland sous.

Le troisième chapitre est consacré à la fixation d’azote par les Cyanophycées

symbiotiques des ltchens, des Azolla et des Anthoceros. Remarquons spéciale¬

ment les communications de W.D.P. STEWART & G. A. RODGERS : Studies on

the symbiotic blue-green algae of Anthoceros, Blasia and Peltigera et de J H

BECKING: Ecological and physiological adaptations of Anabaena in the Azolla-

Anabaena azollae symbiosis.

Le quatrième chapitre est réservé aux bactéries fixatrices d’azote.

La snnple énumération de ces communications montrera, nous l’espérons

présente cet ouvrage ’ aussi bien pour Ies aIgologues que pou;

Rappelons la réimpression, dans la même série, d’un intéressant ouvrage

consacre aux cycles de l’azote, du phosphore et du soufre : Nitrogen, Phosphorus

SVFN«™ r »"H G0l l d [ CyCeS ' Ecological Bulletins, n“ 22, NFR Stockholm,

i9T4oT w .^;b" DERLUND R ed - : 192 p - 1976 ’ 2nd ^ «*■

KUROKAWA, S., 1979 - Studies on Cryptogams of Papua New Guinea Aca-

demta Scientific Book Inc., Tokyo: 150 p.

Ce volume présenté par KUROKAWA groupe une série d’études faites sur le

materiel récolté en 1975, lors de l’expédition botanique japonaise en Nouvelle

Guinee. En algologie nous trouvons quatre articles :

OUVRAGES REÇUS POUR ANALYSE

277

1. - Les algues d’eau douce: algues filamenteuses vertes par T. YAMA-

GISHI et M. WATANABE avec 44 taxons dont Cloniophora plumosa et Cylin-

drocapsopsis indica. __

2. — Desmidiées de Woitape par M. WATANABE, G.W. PRESCOTT et Y.

YAMAGISHI. Les auteurs signalent 45 taxons avec des nouveautés pour les

genres : Cylindrocystis, Closterium, Spinoclosterium, Euastrum, Cosmarium

et Staurastrum.

3. — Les Cyanophycées d’eau douce par M.M. WATANABE, M. WATANABE

et T YAMAGISHI avec 49 taxons dont Rivularia vieillardii.

4. - Le dernier article de S. WATANABE est consacré aux algues du sol.

L’auteur obtient 13 taxons en culture dont une nov. sp. de Chlorella (Palmello-

coccus) et une de Gloeocystis (Palmogloea).

Cet ensemble, fort intéressant pour une région encore très mal connue, est

soigneusement illustré, mais' il est dommage que la répartition géographique

des algues identifiées ne soit pas indiquée.

MATVIENKO, O.M. et DOGADINA, T.V., 1977 - Visnatchik prisnovodnich

vodorostej Ukrainskoj, R.S.R. - III, 2 - Pyrrophyta. Kiev, 1 vol. rel.: 386 p.

Dans ce volume, les auteurs décrivent et figurent les espèces de Pyrrophytes

connus d’Ukraine. C’est en quelque sorte une «Süsswasserflora» régionale.

Ce volume est consacré aux Chloromonadines, Cryptophycées, et Dinophycées.

L’embranchement Pyrrophyta est divisé en 3 sous-embranchements Chloro-

monadophytina, Cryptophytina et Dinophytina.

Les Cryptophytina groupent deux classes : Cryptomonadophyceae et Crypto-

coccophyceae et les Dinophytina cinq classes -.Dinorhizophyceae, Dinomonado-

phyceae, Dinocapsophyceae, Dinococcophyceae et Dinotrichophyceae. Cette

hiérarchisation ne nous satisfait guère, car il s’agit, à notre avis, d’ordres qui sont

élevés au rang de classes.

De plus les Chloromonadines très proches des Xanthophyceae n ont pas

leur place dans les Pyrrophytes.

Le livre, bien illustré, mais avec très peu de dessins originaux rendra des

services aux algologues pouvant lire et comprendre l’ukrainien.

MATVIENKO, O.M. et DOGADINA, T.V., 1978 - X - Xanthophyta. Kiev,

1 vol. rel.: 511 p.

Comme dans le volume précédent, les auteurs relèvent d’un cran la hiérarchie:

les Xanthophycées forment un embranchement des Xanthophyta avec 6 classes:

Xanthorhizophyceae, Xanthomonadophyceae, Xanthocapsophyceae, Xantho-

coccophyceae, Xanthotrichophyceae , et Xanthosiphonophyceae. Pour nous,

ces classes sont des ordres. ,

Signalons que les auteurs rangent dans les Xanthophycées les Microthammon

(d’après SKUJA, 1956, qui ne justifie pas cette place) et Actidesmium : ces

algues à zoospores à deux flagelles égaux et à réserve d’amidon sont des Chloro-

phycées. , . . n . .

Malgré cela, ce volume nous renseigne de façon très précisé sur la flore ukrai¬

nienne et son illustration sera précieuse pour les espèces endémiques de cette

région.

278

OUVRAGES REÇUS POUR ANALYSE

MONTGOMERY, R.T., 1978 - Environmental and ecological studies of the

benthic diatoms communities associated with the coral reefs of the Florida

Keys. Ph. D. Thesis, Florida State Univ. Coll Arts Sci., vol. I: 320 p., man.

MONTGOMERY, R.T. and MILLER III, W.I. -Ibid., A Taxonomie study of

Florida Keys benthic diatoms based on scanning électron microscopy. Ibid

vol. II: 204 pl., man.

La première partie de ce travail est consacrée à l’étude de l’environnement

et de l’écologie des communautés de diatomées benthiques associées aux récifs

coralliens de la côte de Floride. L’auteur analyse la composition spécifique et

la structure des communautés des populations de diatomées de divers habitats

des Florida Keys. Ces habitats sont riches en diatomées mais chacun est carac¬

térisé par une flore propre comme en témoignent les indices d’affinité. Sur les

substrats coralliens proprement dits, les densités de diatomées sont plus impor¬

tantes sur les parties mortes que sur les parties vivantes ce qui laisserait supposer

que, continuellement, le corail vivant se débarasse des diatomées épibiontes

Les études de peuplement de 5 types de substrat, placés dans des habitats

colonises par des Thalassia et par des madrépores, montrent qu’il existe une

relation positive entre la diversité spécifique et la complexité de l’habitat :

celui-ci semble être le facteur réglant la composition et la structure des commu¬

nautés benthiques. Les modalités de peuplement des substrats coralliens, net¬

toyés de toute matière organique puis replacés dans le milieu, indiquent que la

composition spécifique, plutôt que la densité, est le facteur dominant dans la

détermination du degre de compétition au cours de la colonisation d’un sub¬

strat Sur des supports en plexiglas, à la différence des études antérieures, le

nombre d’especes n’augmente pas proportionnellement à la surface de peuple-

ment; neanmoins, cet accroissement de la surface influe sur la composition

spécifique et sur la structure des communautés de diatomées.

La deuxième partie, réalisée en collaboration avec W.I. MILLER se présente

comme un album photographique des divers taxons de diatomées benthiques

recoltees dans les Florida Keys. Ces nombreuses microphotographies, il y en

a plus de 1600, ont toutes été réalisées en microscopie électronique à balayage

et sont d une qualité remarquable. Les auteurs présentent ainsi un nombre

considérable de taxons dont l'identification est soit complète soit incomplète

et ouverte. Sous cette forme il s'agit là d’un remarquable outil de travail dont

utilisation se trouve facilitée par la présence d’un répertoire alphabétique

des divers genres et espèces.

u,r E rVo° nClUSi0n k tra lf de MONT GOMERY, auquel a collaboré en partie

MILLER, est remarquable par la quantité d'informations tant écologiques

qu iconographiques qu'il livre à tous les diatomistes, et en particulier à ceux

travaillant sur les écosystèmes récifaux. Malheureusement, et nous souhaitons

que ce ne soit que temporaire, cet ouvrage volumineux ne figure qu'à l’état

de manuscrit tire à un nombre réduit d’exemplaires. Ces deux volumes doivent

e re suivis d un troisième consacré aux descriptions taxinomiques, nous l’atten-

dons avec impatience.

OUVRAGES REÇUS POUR ANALYSE

279

PARA, O.O. et GONZALEZ, M., 1977 - Desmidiacéas de Chile III. Desmidia-

céas de la Isla de Chiloé. Gayana, Bot., 34: 103 p.

Dans cette île chilienne, les auteurs reconnaissent 150 taxons, dont 47

sont nouveaux pour le Chili.

Les Closterium avec 32 taxons, sont les plus nombreux, suivis par les Stau-

rastrum 29 et les Cosmarium, 28.

Une illustration abondante de 235 figures, suivie d’un index, terminent

cet inventaire descriptif.

SIMONSEN, R., Ed., 1979 - BAC1LLARIA. International Journal for diatom

Research. J. Cramer print., vol. 2: 214 p., 10 fig., 38 pi-, relié, 60 DM.

Après BACJLLARIA 1 paru en 1978, voici le deuxième volume de cette revue

destinée aux seuls diatomiStes. Le sommaire comporte 7 articles dont le plus

volumineux est celui de SIMONSEN : The diatom System: Ideas on Phylogeny.

L’auteur expose ici ses conceptions sur la phylogénie des diverses familles de

diatomées, conceptions qui se sont développées et précisées au cours des der¬

nières années comme en témoignent ses exposés au cours des deux derniers

Symposiums sur les diatomées d’Oslo et d’Anvers. SIMONSEN conserve la divi¬

sion classique en deux ordres, les Centrales et les Pennales, eux-mêmes divises

en cinq sous-ordres et 21 famÜles. Cet intéressant article est complète par deux

appendices: une clef d’identification conduisant aux familles et une classifica¬

tion des diatomées. Cette classification n’est pas sans intérêt mais ne sera pas

adoptée par tous les diatomistes, en particulier en ce qui concerne la division

des Pennales qui, de quatre sous-ordres, est ramenée à deux sous-ordres seule¬

ment: les Araphidineae et les Raphidineae. La raison de cette modification

est l’importance injustifiée accordée, par les précédentes classifications, aux

Raphidoidineae et aux Monoraphidineae. Si l’on suit le raisonnement de l’auteur

l’on ne comprend pas, alors, la fragmentation de certains genres peu représentes

comme le genre Attheya, 3 espèces seulement, scindé en deux sans que cela

apparaisse vraiment nécessaire.

Parmi les autres articles de BACILLARIA 2 citons plus particulièrement

ceux de G.R. HASLE : Thalassbsira decipiens (Grun.) Jorgensen; R. A. G1BSON:

Protoraphis athntica sp. nov., a new marine epizoic diatom; W.H. HOLMES

et A.L. BRIGGER: The marine fossil diatom genus Entogonia Greville. L article

de H. LANGE BERTALOT, Simonsenia : a new genus with morphology inter-

mediate between Nitzschia and Surirella, présente également un grand interet

car la création de ce nouveau genre, intermédiaire entre les Nitzschui et les

Surirella, ne manquera pas de soulever à nouveau les nombreux problèmes

taxinomiques posés par de nombreuses Nitzschia à l’exemple de N. delogne, :

citons par exemple le cas de N. apiculata.

Ce deuxième volume de BACILLARIA tient les promesses du premier,

grâce aux efforts de son éditeur, et sera du plus grand intérêt pour ses lecteurs.

WATANABE, Masayuki, 1978 - A taxonomie study of the Closterium cah-

sporum Complex (l)-2. Bull. Nat. Sc. Mus. Tokyo, Sér. B (Bot.), 4 (4):

133-154 et 1979: id. 5 (1): 1-23.

280

OUVRAGES REÇUS POUR ANALYSE

L’auteur étudie, dans la nature et en culture, 35 clones de Closterium du

groupe calosporum. Grâce à ces cultures il peut évaluer, statistiquement, les

variations des cellules végétatives et des zygotes en fonction des milieux nutritifs

et de la température.

Il peut ainsi reconnaître, et décrire avec précision dans ce complexe à côté

de C. calosporum Wittr. var. calosporum, 2 variétés dont l’une nouvelle, ainsi

que 3 variétés nouvelles de C. spinosporum Hodgetts. Il décrit de plus une nou¬

velle espèce.

L excellente illustration en 11 planches, et les diagnoses très précises des

divers taxons étudiés permettent de mettre de l’ordre dans ce groupe difficile.

Commission paritaire N° 28588 - Dépôt légal : n° 659 - Octobre 1979 - lmp. Vial, 91410 Dourdan