~ I I ;.. ,1 i /., i \ , ,i ,j.:~ 1~ 1;" ~') 1~ ~\ ~ j I .... . ..... , , 1 ,I By " . " , . \. ~ - M. T. PHILIPOSE J I o " "t' ! I ... I "'"""" ICAR -..:.. ,. .' INDIAN COUNCIL I' " OF AGRICULTURAL NEW DELHI RESEARCH { I 1 __'8 r t. c.-.' . ., \ ' ~. ,II~~~l(rc .,..,t~~ ~ [ /! FIRST PRINTED DECEMBER 1967 -~ \ \..'.. PREFACE Chief Editor Editor Subeditor C. G. RAGHAVAKURuP P. KACHROO M. ARIF The present account includes all the known Chlorococcales froni the Indian region comprising India and Sikkim, Pakistan, Afghanistan, Nepal, Burma, and Ceylon. It is dealt with in two parts, the first part giving a general' account of the order, viz., the morphological, ecological, physiological and applied aspects and the classification including phylogeny; and the second part dealing with the taxonomy of forms known exclusively from the Indian region. In writing out this volume standard works on algae like Kuetzing (1843, 1845, 1849), Naegeli (1849), Braun (1855), Reinsch (1867), Rabenhorst (1868), Lagerheim (1882), Hansgirg (188.6), De Toni (1889), Wille (1897, 1909), Oltmanns (1904, 1922-23), G. S. West (1904, . 1916), Brunnthaler (1915), Printz (1927), West and Fritsch (1927), Smith (1933, 1950,_1951), Fritsch (1935), Tilc;len (1935), Prescot! (1951), Tiffany and Britton (1952), Korshikov (1953), Fott (1959), and a number of other works dealing specially with this order have been fully made use of, mostly in original. For the second part, all possible literature on Indian Chlorococcales has been consulted. Apart from these, the author's unpublished observations on the planktonic Chlorococcales of Indian inland waters collected over a period of 25 years hav~ been incorporated in the general Prodmtion Officer : KRISHAN KUMAR ~ ..... -r' t) 3066°9 T .', I. "- ( I I r , - I I and taxonomic part. . @ All Rights Reserved ~ 1967, by the Indian .Council of Agricultural Research, New Delhi 1" . In addition to the genera and species reported from India, a list 'of genera and species of the Chlorococcales not yet reported from India but known from other parts of the world is given at the end of each fanuly with, as far as possible, original referenceS for each. It is not the object of !his work to attempt any new classification or new interpre~tio~ of available, information on the order. The main object as in the case of the rest 'of the monographs in the Indian Algae Serits, is to bring togethe.x:all scattered information on t\1e order for the- benefit of post-graduate and research students, fishery biologists and others interested in the subject. . The- author wishes to express his indebtedness to : (I) Late Pro£: M. O. P. Iyengar, Madras, his esteemed Professor, who initiated him into the field of algology and who had been a valuable source of inspiration in the undertaking of this compilation. (2) .Dr B. S. Bhimachar, Director, Central Inland Fisheries Institute, Barrackpore,. for kindly permitting the author to take up this work, his keen interest, in its completion and for kindly according the necessary permission'to"publish the same. (3) Dr M. S. Randhawa, Adviser, Planning Commission, New Delhi, for his keen interest in the present work, for many valuable suggestions and encouragement at every step. ~ \ I I '1 r I \ Printed in India by M. C. Khunnah at the Job Press Private Ltd., Kanpur, and published by T. S. Pruthi, Under-Secret~.: Indian Council of Agricultural Research; New Delhi. J VI CHLOROCOCCALES (4) for kindly a number (5) Institute, Professor T. V. Desikachary, University Botany Laboratory, Madras, giving the author a number of valuable suggestions and helping with of references and photographs. Dr G. S. Venkataraman, Botanist, Indian Agricultural Research New Delhi, for help in taking a number of photostats of text-book . I \" CONTENTS PAGE illustrations. (6) Rev. Fr. Santapau, Director, Botanical Survey of India, for thel.~tin translations of diagnoses of new taxa included in this monograph. The author also wishes to express his special gratitude to Prof. B. Fott of Prague in helping the author to procure a copy of Korshikov's (1953) work, and in generously supplying reprints of a number of his own papers. The author is also thankful to several European and American authors, notably Prof. H. Printz of Oslo, Prof P. Bourrelly of Paris, Prof F. Chodat of Geneva, Prof T. Hortobilg)6.. of Budapest, Prof. R. C. Starr of Indiana, and Dr F. R. Trainor of Connecticut for being kind enough to supply reprints of some of their valuable papers. CENTRAL INLANI) CUTI'ACK FISHERIES v I , I . I M. T. PHILIPOSE . < ... Preface Chlorococcales Morphology Reproduction Cytology and life-history Ecology and physiology ., Economic importance Classification and Phylogeny Historical Synopses of the families .. Genera of the Chlorococcales Indian Chlorococcales Chlorococcaceae Chlorococcum' Trebouxia ., Characiosipnonaceae CharaciosiPltim Characiaceae Characium .. Korshikoviella Schroederia ., 1 1 15 28 31 51 54 54 65 66 69 72 72 75 I I . .' 78 78 ! .. 81. 81 87 89 94 94 96 98 98 101 103 103 106 106 107 108 108 III 111 111 I \I i I I Chlorochytriaceae Chlorochytrium - Kentrosphaera .. Micractiniaceae ,Trochiscia _' . Golenkin{a. '. Golenkiniopsis Micractinium .. Treubariaceae Desmatractum Treubaria ., Pachycladon ~ r' ConococcUS ., .. '" " Hydrodictyaceae ., Hydrodictyoideae Pediastrum .. J I viii Sorastrum .. Hydrodictyon Tetraedronoideae Tetraedron Ciosteridium Polyedriopsis Oocystaceae Lagerheimioideae Lagerhei ., Chodatella .. Dendrocystis Chiorelloideae Chiorella Paimellococcus Eremosphaeroideae Oocystaenium Oo~ystoideae Gioeotaenium Oocystis Giaucocystis NePhr.ocytium Radiococcaceae Dispora .Botryo'coccaeeae Botryococcus Dictyosphaeriaceae DictyosPhaerium Westella DimorPhococcus I t IX 237 242 245 245 290 293 293 308 324 345 Selenastraceae Dactyiococcus -. . Ankistrodesmus Quadriguia Ciosteriopsis Actinastritm Seienastrum Nephrochiarrrys Kirchneriella Gloeoactinium .. .. ... Coelas traceae Coelastrum Burkillia Scenedesmaceae Crucigenioideae H~nia .. 132 Crucigenia .. 133 I, Tetrastrum . . 136 ~enedesmoideae 136 Scenedesmus 161 ~ Tetrallantos 164- 'enera of Uncertain Systematic Position 166 Elakatothrix 167 ddendum 167 ib1iography 168 ndex .. 171 '72 172 176 177 177 178 178 179 187 189 193 193 195 195 199 199 203 204 208 .208 210 215 216 1\ 217 218 221 222 225 227 227 234 236 236 236 \.~m3 '*" ..( -.. j I. :,1· Order CHLOROCOCCALES March and Orth. mut. et emend. Pascher, 1915 ~ t J MORPHOLOGY Members of this order are found mostly in 'freshwater and are free living, tached, endophytic or endozoic. A few forms also Occur in brack':sh water, ~n moist 'OIs,walls and on tree trunks, especially in exudations of sap. Some species of_ 'oreLl.'1.. cJ.[tnochytrium, haracium, Oocystis, and Sykidion are marine. Scotiella has been C ordel mainly as a constituent of snow floras, whereas some species of Scenedesmus known to tolerate temperatures as high as 50-63°C obtaining in hot springs. rely, members of the order are parasitic or live in symbiotic association with fungi lower groups of animals. _ _ The predominant phase in the life-history is a non-motile one. Formation of 'spores or gametes may take place at the time of reproduction, but these swarmers short-lived since they come to rest soon after their- liberation and remain p~ive ing a prolonged period of vegetative growth before giving rise to motile cell~ again. :getative- dIvision of cell is absent altogether or occurs only very rarely, the only cell ision thar- takes place being at the time of reproduction. The algae belonging to CWorococcales are unicellular, coenocytic or colonial ',g. I, a-p). In its simplest form a CWorococcoid cell is unicellular and uninucleate in Chlorococcum, where sometimes, as in C. -humicolo and C. olivaceum,he swarmers t t are liberated come to rest side by side and the resulting cells become crowded and a stratum which has the false appearance of a colony. Occasionally, the cell also be multinucleate, as in C. multinucleatum. In Chlorochytrium,PhyLlobium,and 'dochytrium,he.unicell is coenocytic and irregularly lobed or in the tbrm of branching t ads. The protocoenocyte of Characiosiphon usually club-shaped .and a number of is occur in clusters. Sometimes, as in Chlorella and Ank~strodesmus,a number of are loosely aggregated with or without the aid of mucilage to form regular or lar colonies.. I~ Chlorel~a,which is usually colonial, sometimes solitary, this egation is with the ~id of mucilage; whereas in Ankistrodesmusit is usually without aid of mucilage. In Selenastrumalso, the cells of the colony are in ,contact along of their surface. In Gloeotaenium,a two to four celled compact colony is formed onnecting mucilage pads. In some others, particularly NePhrocytium, Oocystis allied genera, a simple type of colony is formed by a number of cells becoming osed within the parent membrane which becomes gelatinized. NePhrochlamys nastraceae), on the other hand, has cells enclosed within a non-gelatinizing t cell membrade. A number of other genera, like Radiococcus,Kirchneriella, 'actin~um and Tetrallantos,are also colonial and enclosed by a mucilaginous envelope, { ..r~ .1 ' y# . J1 . .,'1 ; "" - '11\1\'- ,iI ~ , ' b l 11\ ) 41\~ ,; -~J . '~... ~~~ r' , ~ ':;, J ~ / MORPHOLOGY CHLOROCOCCALES 'f 3 .. ',.,. '. .~... .' ,.' .', . ~~;t;j~ c . Ih I I I I I I /...~...@ \ /m. ~k \.~~j \ . which is usually visible 'Only after staining. In the Dicty'Osphaeriaceae the individual cells 'Ofa c'Ol'Onyare held t'Ogether by filif'Orm branches f'Ormed by the parent cell 'membrane, and the c'OI'Onies-areregular (Dictyosphaerium)'Orirregular (Dimorphococcus), Iwith 'Orwith'Out a c'Omm'Onmucilagin'Ous envel'Ope. In the c'Ol'OnialHydr'Odictyaceae, the c'Ol'Ony in the f'Orm 'Ofa net-w'Ork, as in Hydrodictyon,or in the f'Orm ~Ta regular is 'flat disc, as in Pediastrum,'Orit is a spherical c'OI'Ony, in Sorastrum. In the C'Oelastraceae, as I,thec'Ol'Onies re usually regular and spherical as in m'Ostspecies 'OfCoelastrum'Orirregular a s in Burkillia. In the Scenedesmaceae, the c'Ol'Onies ay be quadrate, as in Crucigenia, m r rectangular with the cells arranged in a single linear 'Or d'Ouble linear series, as in 'cenedesmus. In Crucigenia,Coronastrum,Hofmania, and s'Ometimes in Coelastrum,multiple 'OI'Onies, n which a number 'Ofc'Ol'Oniesare held t'Ogether by lateral c'Ontact 'Or by i emnants 'Ofthe parent cell membrane, are frequent. In Actinastrum als'O, multiple 'Ol'Onies are 'Occasi'Onallyf'Ound (Fig. I, I) but the individual c'Ol'Oniesn this genus are i eld t'Ogether 'Onlyby lat~ral c'Ontact. Pectodutyon(Fig. XVII, I) is an interesting enus in which the c'Ol'Ony a cubical frame-w'Ork 'Ofgelatin'Ous strands with a single has herical cell at each 'Ofthe eight c'Orne~ 'Ofthe frame.~w'Ork. A number 'Ofsuch frame'Orksj'Oined t'Ogether give rise t'Oa multiple c'Ol'Ony 'Orsync'Oen'O.bium. In Botryococcus, cells are embedded in thimble like envel'Op~st'O f'Orma the mewhat radiating c'OI'Ony, nd a number 'Ofsuch c'Ol'Onies a may be held t'Ogether by .ugh mucilagin'Ous strands. 'I}1e c'Ol'Ony Nephrocytiumecdysiscepanum in the f'Orm 'Offan-shaped aggregates. in is ere the membranes 'Ofdividing cells bec'Ome thick and stratified,.with the 'Outer layers maining~. The outc!r layers then split 'On'One~ide while the inner -layers, which cl'Osethe'cells, bec'Ome gelatinized. When the daughter cells divide again the same 'Ocessis repeated, the entire structurel'O'Oking like a fan-shaped aggregate (Fig. I, '0). is type 'Ofc'Ol'Ony f'Ormati'Onsh'Owss'Ome anal'Ogy t'O th'Ose in the Dicty'Osphaeriaceae d the Chl'Or'OdendrineaeV'Olv'Ocales), ( particularly t'Othat in EcballocystisseeFritsch, ( '35, p. 160). A dendr'Oid type 'Ofc'Ol'Ony als'Of'Ormed.in Ankistrodesmusfalcatus var. is itatus(Fig. I, n). Iyengar (1962) has recently rec'Orded a new genus, Dendrocystis, which ~he cells are dendr'Oid as in Ecballocystis but many 'Of its: cells p'Ossess " " A -y ines as in Lagerheimia. In Dactylococcus, a number _ . 'Of cells are placed end t'O end t'O farm a branched FIG. 1. RANGE O' 1'I1"U.\II a, ChlorocOccum echinozygolum STAJUl; b, C. OIlH"lIm RABENH.; c. SClnetllm1u1 ,¥lithii TElLiNG VAR. linea~-VAR. NOV.; d, lWllU/rum IIlras (EHl!-') RALJI; ... CharluioJiphon rivularis IYSNG.; f. RJwdoe!r1IriNlft 'JlI/IlIt/hidiJ LAOERg.; g. ~IIU/tIIJII .~nI VAR. inler7ntdium (B..oHLlN).G...S: Wanl h, GIOlOltunium loilllsbng,,;anum \,"~O.I I, DimorphococCUJ IWUlIUI A.. ISM""I j, $,ltnClJlrum gre"i" RBlNSCII.; ent'Ous c'Ol'Ony(Fig. I, k). The s~ape 'Ofthe cell als'Ovaries c'Onsiderably within the Ol:der (Fig. II, a-z, a.-I.). may be spherical (Chlorococcum, hlorella, Golenkinia, etc.), 'Obl'Ong,ellips'Oid 'Or citriC (Oocystis, Lagerheimia, Chodatella), 'Ov'Oid-ellipsoid, plan'O-c'Onvex, 'Or renif'Orm tyosphaerium), 'Ob'Ov'Oid, yrif'Orm, fusif'Orm 'Or lance'Olate (Characium), cylindrical p drodic~on), club-shaped (Actinastrum), fusif'Orm, navicul'Oid, 'Obl'Ong-ellips'Oid"bicave, prismatic, 'Orarcuate (Scenedesmus),acicular, spiral 'Orc'Onv'Olute(Ankistrodesmus), orm 'Orsigm'O,id(Schroederia),cuneif'Orm (Burkillia, Gloeoactinium),'Obl'Ong-cylindrical (a, FROM STARR, 1955; b, AFTER HODGETTS, 1926; c, j, m, ORIGINAL; d, FROM G. M. SMITH, 1920; e, AFTER IYENGAR, 1936; f, AFTER LAGERHEIM; g, AFTER STOCKIdAYER;e...h. AFTER RICH, 1932; i, AFTER WEST; k, FROM G. M. SMITH. 1950; I, p. AFTERX::;.M. SMITH, 1920; n, AFTER CHODAT; 0, AFTER WEST). c, j (x 725) AND m (X 1500). N.B.-All figures in this and subsequent pages reduced to about two-third the original lae. '~ ,~'1 (~ ~ NASG.;I, .If:::':::' ~'"'.c'thii LAGERH.: . Kirch"'"" m ""tor". (SCH)&!DLE) Bo~; p,.If ut._ III /tl.,./tI, VAR.JlipilahU (CilOIJ.) . ,.,101.' 0, Nephroeyliumecd.1ns~1SIfI !~, I \), ~clJon r,lifulCJl1llll (1..) . j~"4t1 OCCUJ infusionum I)'/OC l>fJ& \..,('8"'" ;: I~ ,. -.. ~8L. r 4 CHLOROCOCCALES MORPHOLOGY 5 Q Q 0, h ~y I~ G>, @ 0 /t Q ~" 0. ~p rIJ or cordate (Dimorphococcus),reniform to cordate (Sorastrum), semi-lunar or vermiform (Kirel/TIeriella),sickle-shaped (Selenastrum), sausage-shaped (Tetrallantos), triangular, Ruadrate, tetrahed!~l, cruciate or polygonal (Tetra~dron)or ovate, polygonal or H-shaped (P,diastrum). In Dlmorphocorcus, as the .na~e Itself suggests, there are two types 'o{ce1lsin the same colony, one oblong-cyhndrIcal and the other sub-cordate to cordate. f !The shape of cells might also vary .with age, the older cells having a shape which is frequently different from that of the young cells. Cell wall.. As in other members of the Chlorophyceae, the cell wall " .. (F.ig. "III, a-z) is mainly composed of cellulose, but sometimes pectose layers of ~lilmuciIage are developed external to the cell membrane proper. to"i' In the simpler forms of the Chlorococcales, as in the Chlorococcaceae, the ,., [J 0" Q a0 v" 0 tJ .d/ W Q ~.\2 ~, !;£ ~ "b'~;, .~... DfJ~, j I FIG. II. CELL SHAPES(CONTENTSNOT SHOWN) a, Chlorococcum (SPHERICAL); b, Coelastrum microporum. (OVOID); c, OO'Y!tis (ELLIPSOID); d, Dictyosphaerium ehrenbergianum (OVOID-ELLIPSOID); c, Characltnn. debaryanum (OBOVOID); f~ C. orissicum (PYRIFORM); g, Hofmania lauterbornn.(SEMI-SPHERICAL);h, Scenedesm!ls quadricauda and i, Dimorphococcltsfritschii (OBLONG-CYLINDRICAL); j, Hydrodictyon reticulatum (CYLINDRICAL); k, Characium ambiguum (LANCEOLATE); I, Pediastrum ovatum (OVATE); m, Ankistrodesmusfalcatus (ACI?ULAR); n-o, Scenedesmus dimorphus and S. obliquus (FUSIFORM);p, Actinastrum hantzschil (CLUBSHAPED); q, Scenedesmus perforatus (BICONCAVE); r, S. carinatus (NAVICULOID); s, Burkillia cornuta (CUNEIFORM); t, Dictyosphaerium indicum (p~~O-CONVEX); u, Scenedesmusprismaticus (PRISMATIC);V, Sorastrum spinulosum (CORDATE REN1FO~M); TO W, Selenastrum gracile (SICKLE-SHAPED); x, Scenedesmus arcuatus VAR. capt/atus (ARCUATE); y, Dictyosp~aerium reniforme (iNIFORM); 4> ~:eUmembrane proper is usually smooth, thin and close-fitting in young cells, frequently 'becoming thicker in old ones. However, in the vegetative cells of Chlorochytrium,the jpunetangfa of Phyllobium and the resting cell of Kentr~sphaera, all belonging to the ~orochytriaceae, the cell wall is thick and stratified. The lamellation of the cell wan is sometimes seen in other families also. Thus, in the vegetative cells of ~lttunella and E~centrosphaera(Oocystaceae) and the old cells of Burkillia..dissolvensSkuja :(Codastraceaeh the outer wall is thick and layered. CharaciosiPhon (Characiosiphon~«i:eae)has a firm. lamellated outer wall. In Hydrodictyon indicum Iyengar, the cell is not only lamella ted, but has u:.o knob-like projections into the protoplasm. )n Desmatractum(Treubariaceae), the cell wall is in the form of two envelopes, one '.~~imuiediately exterior to the protoplast and close fitting--and the other in two pyramidal ~ves, the space betw~en the two being filled Fith mucilage. The pyramidal halves 'C also joined at the median portion and are provided with longitudinal ridges. In ,:iiI/la (Oocystaceae), the longitudinal ridges are spirally twisted. KeriochlamY.f._Pascher i)in interesting alga in whIch the cell wall is thick with a number of refractive bodies' ,,~'P.unknownnature embedded in it, giving it an alveolar appearance. . ( Recent studies with the electrone microscope (Moner, 1955; Desikachary, 1957) '.~~ve shown that eyen in Pediastrum the apparently simple cell wall is made up~o .~Yers, a continuous internal membran~ and a hexagonally reticulate outer layer:- , ~~, also.. easo!}'s (1961) detailed study of the structure and composition of the cell_ D ~allof several genera of Chlor~coccalean algae, using stains and employing micro~eDlical analys-esj.. . ,. ~n 1 1 1 \ I I ,. t. According fo Parker (1964), who investigated tJie structure and chemical compo:~.iionof three Chlorophycean algae, the cell wall of Pediastrum tetras contains a crystal~littepolysaccharide composed of D-glucose and D-mannose which forms a non'p!i9'ofibrilIar net-work of interwoven chains of rings. The cell wall polysaccharide is ~.ther a gluco-mannan or aglucan intimately associated with mannan. .' A large number of Chlorococcales, unicellular as well as colonial, have their cell ~ ornamented in different ways. . The simplest form of ornamentation is seen in .(VERMIFORM); a" Dimo~ph0!J!C.CI{S. fritsch~i (CORDATE); b" Tetrallantos lagerhe~mii (SAUSAGE-SHAPED);c" Kzrchnerzella lunarzs. (SEMI-LUNAR); d" Tetraedronmutzcum (TRIANGULAR); c" T. pusillum (CRUCIATE); f,; Pediastrum duplexvAR. gracillimum (H-SHAPED); g" Schroederia setigera (SIGMOID); h" Ankistrodesmus convolutus (CONVOLUTE); i" A. spiralis (SPIRAL); j" Tetraedron quadratum (Q.UADRATE);k" T. minimum (TETRAHEDRAL);Ir, Pedirzstrum muticum (POLYGONAL). .. I z, Kirchneriella contorta _,J' ~CHLOROCOCCALES MORPHOLOGY 7 .,0 a b d Gh ~ , . m ~ .q I, g w ~. - ~. W FIG. Ill. CELL WALL, ITS LAMELLATIONS, ORNAMENTATIONS, AND MODIFICATIONS OUT-GROWTHS, x -.. ;- - - cell walls which are finely punctate, coarsely granulate or verrucose. A number of species and varieties of Tetraedronand Pediastrumthus exhibit cell walls which range from punctate to coarsely granulate. A similar cell wall may be present in Cerasteriasand some species of Scenedesmus. In Trochisciaand some species of Pediastrum, the ornamentation is in the form of a net-work of ridges. In the latter genus the cell wall may also become undulate to rugulose, especially where it adjoins the wall of another cell. In Mycacanth'%coccus Hansgirg, the cell wall is verrucose or spinous on the outside. In a number of other genera, short or long spines or bristles are formed from the exterio~ surface and these are usually solid. The spines of Tetraedronand Scenedesmus usually are short or long, whereas the spines or setae of Treubaria (incl. Borgea) are very long and someti~es gelatinous. Bristles, are usually seen in unicellular genera like Golenkinia, Golenkiniopsis,Polyedriopsis,Chodalella, Lagerheimia and Franceia and the colonial genera Micractinium (incl. Errerella Conrad) and Palmellochaete,the number and position of the bristles varying with the genera. In Echinosphaerella,the spines are more or less gelatinous. These spines anq bristles are usually associated with the' pelagic habit of the forms concern~. The parent ~~ll membrane sometimes becomes partially gelatinised at the - time of reproduction -and -forms an envelope for the daughter cells, as in Oocystis. In Gloeotaeniumthere is not only an outer mucilaginous envelope, but th~re are also bands of mucilage betWeen -the cells of colonies with apical and equatorial caps for the cells. The outermos't layers .of this envelope contain refractive calcit~. .' The.!e are also other genera like Kirchneriella, Gloeoactinium, adiococcus, R _COetlOCOCCUS, Coeiiochloris, Coenocystis, Dictyosphaerium Hofmaniain which there,is an outer colonial mucilaginous envelope, and and it may be lamellated as in DictyosPhaerium pulchellum. In Hofmania,rupturedfragments of the- parent cell membrane as well as the mucilage remain outside the new colony. These mucilaginous pectose layers d'iliibit all stages from solubility to insolubility in water and formation of the mucilage probably continues throughout the )ife cycle of an alga (Fritsch, 1935). In the Dictyosphaeriaceae, during autospore formation, th~ parent cell membrane gets fragmented. These roll up and become connecting tl~reads for the cells of colonies. In g~nera like Coelastrumalso, sometimes multiple colonies are held together by contact or by bt;.oken b[ts.. of the parent cell wall. Quite recently, Edelstein and Prescott (t964-) have described. an interesting new genus Rayssiella, allied to Nephrocytium, ~ith the single species R. hemisphaerica, in which autospores which are polar and hemispherically arranged, have interconnecting gelatinous: threads, formed by the dis.tion of the mother cell wall. Protoplast. The protoplast (Fig. IV) fills the cell cavity in young as welt as old cells; or'rarely, it is vacuolate in the centre, as in Chlorococcum vacuolatum.However, - I . a, Tribouxia humicola (TR~BOUX) WEST ET FRITSCH (P-PYRENOID); b, Te/raedron minimum (A. BR.) HANSG.; c, Muriella magna FRITSCH ET JOHN; d, Hydrodictyon indicum IYENG.; e, Ken/rosphaera facciolae BORZI (RESTING CELL); f, Burki/lia dissolDens SKUJA; g, Ceras/erias irregulare G. M. SMITH; h, Trochiscia re/icularis (REINSCH) HANSG.; i-j, Desma/rae/um bipyramida/um (CHOD.) PASCHER; k, Mycacan/hococcus an/arc/icus WILLE; 1, Te/raedron horridum WEST; m, Trochiscia aspera (REINSCH) HANSG.; 0-0, Sco/ie/la antarctica FRITSCH; p, Pedias/rum araneosum VAR. rugulosum (G. S. WEST) G. M. SMITH; q-r, Gloeo/aenium loitlesbergerianum HANSG. (p-p'-POLAR CAPS); S, Keriochlomys styriaca PASCHER; t, Dictyospliaerium pulche/lum WOOD (m-MUCILAGE; t, CONNECTING THREAD FORMED FROM MOTHER CELL MEMBRANE); u, Oocystis g/oeocys/iformis BORGE; v, Golenkinia radia/a CHODAT; -+ ., -+ w, Coe/as/rum 're/icula/um (DANG.) SENN (P-CONNECTING-PROCESSES); SPLIT IN S, THE REMAINSOF THE CELL WALL THROUGHWHICH DAUGHTER COLONYHAS BEEN LIBERATED); x, Hofmania lau/erbo~nei (SCHMIDLE) BRUNNTH. (G-MUCILAGE;W, REMAINS OF CELL MEMBRANES);y, SceMdesmus arma/us VAR. spinosus FRITSCHET RICH; z, Chodatella ciliata (LAGERH.) LEMM. (a, VIZ. AFTER CHODAT; b, AFTER G. M. SMITH; C, FROMFRITSCHET JOHN, 1942; d, FROM IYENGAR, 1925; e, AFTER BORZI; f, AFTERSKUJA, 1949; g, FROM G. M. SMITH, 1950; h, m, AFTER WEST; i, AFTER PASCHER; j, AFTER KORSHIKOV; k,FROM KOL; I, AFT~R PRINTZ; n-o, AFTERFRITSCH; p, FROM G.M. SMITH 1920; q-r, AFTER STOCKMAYER; , FROMTHOMPSONIN G. M. SMITH, 1950; t, w, AFTER S SE"N; H, AFTER BORGE; x, AFTER OLT/ofANNS; y, AFTER FRITSCH ET RICH, 1930). 8 CHLOROCOCCALES MORPHOLOGY 9 in some adult cells, as in ErtmosPhaera, the cytoplasm is in the form of a peripheral layer with strands radiating towards the centre, where the nucleus is suspended. The peripheral layer and sometimes the radiating strands contain a number of disc-shaped chloroplasts. In CharaciosiPhon the protoplasm is restricted to the periphery with cell sap in the central cavity. This genus is also peculiar in that there are a number of separate protoplasmic bits one layer thick forming the lining on the inner side of the cell wall, and these bits are far apart at the basal regoin of the coenocyte, whereas they are close to each other in the apical region. These discrete protoplasmic units lying apart are also connected to one another by delicate strands of cytoplasm, not unlike some species of Volvox (Iyengar, 1936). The increase in number of protoplasts are clearly seen in the germlings (Fjg. IV, i-k). ~ . a c PY '~"',;. r. vii: · I.... f. Nucleus. Usually there is only a single nucleus (Figs. IV, XIV) in each cell. In young cells of Chlorococcllm is placed in the region of the notch in the chloroplast. it However, in older cells (Fig. VI, h) or during successive division of the protoplast the number may increase, each bit of the protoplast receiving a nucleus. This increase in number is probably in preparation for the formation of reproductory units (Fritsch, 1935). Examples are species of Chlorococcum, Tr!bouxia, Chlorochytrium, EremosPhaeraand Chlorella. Sometimes, as in Chlorococcummultinucleatum Starr, the mature cells have many nuclei even without accompanying division of the protoplast. The same is tht! case with Ai:tinochloris phaericaKorsh. and Pseudochlorothecium s mucigenum Korsh. (Fig. VI, p; VrrI, i). In ~enera like Tetraedron, Characium, Hydrodictyon,Pediastrum, Sorastrum, Coelastrum and probably Scenedesmus,the mature cells are multinucleate, and, in these algae, simultaneous division of the protoplast into a number of bits takes place, each bit receiving a nucleus. In Characiosiphon there is a single nucleus in each of the naked protoplasmic bits and it is in the strict sense a large coenocyte. Chloroplast. The chloroplast (Fig. V, a-z) typical of many Chlorococcales has been described as 'chlorococcoid' (Fritsch,' 1935). It is.single, parietal a9d in the form of a hollow sphere with an aperture of varying size on one side,. Chlorococcum is humicolo a typical example. According to Starr (1955), t~ parietal hollow sphere is fundamentally cup-shaped as seen in Chlorococcum echinozygotum, C. hypnosporum and C. minutum. In ~ome of the Dictyosphaeriaceae and in species of Chlorellaand Golenkinia, the chloroplast is typically' cup-shaped. This is almost like that obtaining usually in Chldmydomonas. In. Botryosphaera sudetica,. the cup-shaped chloroplast h¥ finger-like lobes at the front c:nd. In' still others, like Characium, Schroederia, Actinastrum -and g h FIG. IV. a, Trlbouxin SP. ; h, Characium PROTOPLAST terres/ris KANTH.; c, Bracleacoecus minor (CHODAT) PETROVA, (a-c, WITH PROTOPLASM FILLING THE CELL; a, UNINUCLEATE; h-c, MULTINUCLEATE); d, Eremosphatrn viridis DE BARY, OPTICAL SEC'lJON SHOWING CENTRAL NUCLEUS AND RADIATING CYTOPLASMIC STRANDS; e-k, CharaciosiPholl, rivu/aris IYENGAR, e, PROTOPLASTS IN THE UPPER PART OF THALLUS; f, P~OTOPLASTS SHOWING PROTOPLASTS (n) NUCLEUS, IN THE (py) LOWER PYRENOID, PART (v) OF VACUOLE THALLUS; h, AND (w) CELL VIEW WALL; g'-h, SURFACE SHOWING PROTOPLASMIC CONNECTIONS; g, IN EDGE VIEW; i-k, GERMLINGS SHOWING 4 TO NUMEROUS PROTOPLASTS;j, IN OPTICAL SECTION SHOWING 5 OF THE 8 PROTOPLASTS AND THE CENTRAL CAVITY. e-k, (a, c, FROM STARR, 1955; h, FROM KANTHAMMA,1940; d, FROM MOORE; AFTER{vENGAR, 1936,1954). NePhrocytium, it is parietal and very' often partially girdling the cell. In Pediastrum, ScenedesmUs, oe/astrumand a number of other genera, the parietal chloroplast is in the C form of a flat band. Sometimes,'as in Characium and Tetraedron, it is parietal in young cells, but becomes rather diffuse in old cells. Though th'e chloroplast in most of the Chlorococcales coi\forms to one of the above cat~gories,. yet in a number of genera and species it is of different nature : in Tre~uxi~, it is axial and massive with the periphery often lobed or wrinkl~; in Chlorochytrium,Kentrosphaeraand Phyllobium, though the chloropl~t is usually parietal and cup-shaped in young cells,)t becomes stellate in old cells and in gametangia, with radial branches' expanding to parietal. lobes; ?tctinochloris.Korshikov, Macrf!chloris Korshikov, Burkillia dissolvens Skuja and CharaciosiPhon Iyengar have also stellate chloroplasts; in Spongiochlorisand Dictyochloris (Starr, 1955), however, it assumes the form of a fine net-work of interlacing strands; and in Hydrodictyonalso, the single chloroplast is in the form of an elongated parietal reticulum. . Electron microscopical studies on the chloroplasts of a number of green algae, including Chlorellaand Ankistrodesmus(Albertsson and Leyon, 1951; Desikachary, 1959) have revealed that, unlike the higher plants, where the chloroplasts have a lamellated structure with thick grana, the chloroplasts of these algae have a uniform structure, without a trace of the grana, and are made up of parallel lamellae about 70-100Ao thick running through their entire length. The lamellae also appear to be bundled in groups of four to eight. Stroma lamellae are absent and the globular stroma I'litl' ~ 10 CHLOROCOCCALES MORPHOLOGY II occurs in relatively thin layers between these lamellae or bundles of lamellae. . An outer membrane, similar to the one seen in the chloroplasts of higher plants, has also been shown to be present in the chloroplasts of the algae, except in the blue green algae (Desikachary, t. c.). The number of chloroplasts in a cell might increase probably in preparation for cell division (Fritsch, 1935) but in a number of genera the presence of more than one chloroplast in a cell is a constant feature. Among the unicellular forms, Dictyococcus, Trochiscia, Palmellococcus,Eremosphaera and Oocystaeniumare examples. Dictyococcus has a number of parietal lenticular or polygonal plates bearing a variable number of centripetally projecting processes (seeStarr, 1955). Trochisciaand Palmellococcus also have usually several parietal disc-like chromatophores. In Eremosphaerathere ar~ numerous discoid chloroplasts in the parietal cytoplasm and in the cytoplasmic strands extending to the centre of the cells. Oocyslaeniummay have as many as 209 lanceolate to irregular chloroplasts in its cells. In Characium, occasionally there may be several parietal chloroplasts. In Oocystis, the number varies from one to many and it may be parietal and laminate (Fig. V, r), stellate, or, when in large numbers, disc-shaped (Fig. V, w). In Planktosphaeria, a colonial planktonic genus, the vegetative cells possess several separate chloroplasts, each with a pyrenoid. In DictyosPhaerium,the number might vary from one to two, and in Cruc:6o,tia from one to four. Characiosiphon has a stellate chloroplast in each of its protoplasmic units. All the types of chloroplasts mentioned above, except the numerous discoid type, are found irithe single family, the Chlorococcaceae. Ho~ever, there are also forms in which the chloroplast or chlorophyll 'is absent altogether. Thus, in Rlwdochylrium Lagerheim, a parasite living on the leaves ofphanerogamic plants, ther~is no chlorophyll, the frequent red colour of the threads being due to oil drops containing a red pigment. Hyalocharacium Pascher, Prototheca Krueger, Mycoletraedron Hansgirg and HyaloraphidiumPascher et Korshikov are further examples of colourless Chlorococcales. They are colourless parallels of Characium, Chlorella, Tetraedron, and Ankistrodesmus res,pectivdy. Gloxidium Korshikov, a member o( the Selenastraceae, Myurococcus Hansgirg, and Mycacanthococcus,(considered by Printz, (1927) and Bourrelly (1959) as- members of the Tetrasporaceae and by Fritsch as probable members of the Chlorellaceae) are also colourless. In Palmellcoccus variegatus the green colour is lost when the alga is grown on organic media like agar. Glaucocystis a colourless member of the Oocystaceae which is. lives symbiotically with a rod-shaped member of the Chroococcaceae (Myxophyceae). The radially arranged chloroplast-;like structure is really the blue green component of the symbiont. The pigments of the Chlorococcales, as in the rest of the Chlorophyceae, are considered more or less the same as those in higher plants, viz., chlorophyll-A, -+ (a,b, d,n, FROM STARR, 1955(d, ASRadiosphaera dissecla (KORSH.) STARR; V, CONTRACTILE VACUOLE); c, FROM CHODAT; e, FROM GRINTZESCO; f, AFTER IYENGAR and BALAKRlSHNAN, 1956 (AS Golenkinia minulissima IVENG. ET BALAKR.); g-h, AFTEIl SKUjA, 1949; i, AFTER IVENGAR, 1954; j, FROM IVENGAR, 1936; k-I-m, FROM GERNECK; 0, FROM MILLER; p-q, FROM A. BRAUN; r, AFTER RICH, 1932; S, AFTER KI.EBS (PVRENOID; N, NUCLEUS); t-u, FROM G. M. SMITH, 1950; v, AFTER KORSHIKOV, 1953; W, AFTER WEST; z, AFTER MOORE). 0 :L ,'" =: .': ...~.. ...:..: e ~, k " v i r _ . 0 ":::)0'" . ~..I'.':'~ ':.-;. ':.: "'1/,:.: ,"" ~':':~':. t FIG. V. CHLOROPLASTS AND PVIlENOmS J ., l a-b, Chlorococcum c, .Trlbouxia humicola (TR~BOUX) WEST ET FRITSCH; d, ActinoSP; chloris sphaerica KORSH.; e, Chlorella vulgaris BEIjERINCX; f, Golenkiniopsis minutissima (ivENG. ET BALAKR.) COMB. NOV.; g-h, Burkillia dissolvens SKUjA; i-j, CharaciosiPhon rivularis IYENG. (i. A GERMUNG; j, AN ADULT CELL); k, Scenedesmus denticulaJus LAGERH.; I-ni, Dictyococcu.s varians GERNECK; n, Dictyochloris fragrans VISCHER EX STARR; 0, ActiJesmium hooken REINSCH; p, Characium sieboldi A. BRAUN; q, C. ornithocephalum A. Br.; r, Oocystis borgei SNOW; s, Hydrodictyon reticulatum (L.) LAGERH.; t-u, Planktosphaeria gelaJinosa G. M. SMITH; v, Botryosphaera sudetica (LEMM.) CHODAT (2 CELLSFROMA COLONY); w, Oocyslis panduriformis WEST; z, Eremosphaera viridis DE BAIlY. -+ 12 CIlLOROGOCGALBS MORPHOLOGY 13 chlorophyll-B, carotin and xanthophyll. One of the reasons why Botryoeoeeushas been brought back from the Xanthophyceae to the Chlorophyceae is that it possesses chlorophyll-B, which is absent in the Xanthophyceae. Apart from the carotin present in the chloroplasts, carotinoid pigments may occur outside the chloroplasts in the form of haematochrome, which is very often dissolved in fat globules (Fritsch, op. c.). Though haematochrome is not very common in the Chlorococcales, ~tmight occasionally occur, as in Botryoeoeeus,Chloroehytriumand Phyllobium. In Palmelloeoeeusminiatus val'. porPhyrea, the pigments phycocyanin and phycoerythrin have also bee~ reported in the chloroplast (Boresch, 1922). Pyrenoid. In most of the Chlorococcales there is only one pyrenoid in each chloroplast, rarely more; but in a few forms there is always more than one pyrenoid in the chloroplast. In some of the forms pyrenoid is indistinct"or absent altogether. The pyrenoid is usually surrounded by a starch sheath, but sometimes is naked as in Botryoeoeeus. In Chloroeoeeum,the single pyrenoid (Fig. V, b) is lateral, being phiced opposite the aperture of the chloroplast. In older and larger cells, it might become several (Fig. VI, h). In Oocystis, usually there are a number of chloroplasts, each with a pyrenoid. The same .is the case with Planktosphaeria and Oocystaenium. In Chiorella (Fig. V, e); the single pyrenoid is either distinct or indistinct, or sometimes there is no pyrenoid. In a nl!mber of other genera, like Tetraedron,Ankistrodesmusand Daetylococcus also, the pyrenoid mayor may not be present. :_ Some of the Chlorococcales possess more than one pyrenoid in the chloroplast: e.g., one to fOlIr per chloroplast in EremosPhaera,and one to two in Desmatraetum. Sehroederiaand CMracium also occasionally show more than one pyienoid in the chloroplast. Eetogeron Dangeard is an interesting epiphyte with numerous pyrenoids. The old cells of Chloroehytrium have a number of pyrenoids scattered in the chloroplast: The reticulate chloroplast of Hydrodic.tyo[l (Fig. V, s) has also a number of scattered pyrenoids-. Genera like Dictyoeoeeus,Dictyoehloris, Gloeoaetinium,Pseudoehlorotheeium, Dendrocystis and a few others do 'not have any pyrenoid. In some of-the Chlorococcales like. Tetraedron,Pediasij-umalld Coelastrumithe single pyrenoid does not divide at the time of cleavage of the -p.rotoplasm to produce daughter cells, but r~!Ilains in one of the bits. This pyrenoid disappears later and each' daughter c~ll develops a new pyrenoid (Geidel', 1924) whereas in, some, like. Chloroeoeeum, Chloroehytrium, Tribouxia, Chlorella' and Dictyosphae;ium, the pyrenoids divide along with successive divisions of the protoplast so that .each daughter cell receives one. Compound pyrenoids consisting of two pieces have been reported by Geidel' (1926) in a number of algae, including Dietyosphaeriumpulehellum. I t has been considered that there are as many sheaths in such algae as there are segments of pyrenoids. Electron microscopical studies of the pyrenoids of green algae (Leyon, 1954; Desikachary, J959)- have shown that, like chloroplasts, they are also lamellated, the lamellae being three; to four times as thick as the chloroplast lamellae and are .continuous with the latter. However, the pyrenoids of Chlorellapyrenoidosa and some other algae fixed in an active state showed only very dense pyrenoids devoid of any internal structure (Albertsson and Leyon, 1954; Leyon, 1954).. , Vacuoles. Contractile vacuoles, normally associated with the motile cells of the Volvocales and of other flagellate algae, are usually absent in the Chlorococcales. However, Apioeoeeus Korshikov, Trigonidium Pascher, some speciesof Chloroeoeeum (including, Hypnomonas Korsh.), SpongioeoeeumDeason and Bieuspidella Pascher and young cells of DesmatraetumbiPyramidatumand Troehiseiaaeieuliferaare characterized by the presence of one to two contractile vacuoles, usually sitUated on one side' of the chloroplast (Fig. VI). In AetinoehlorissPhatricaKorsh., there are several contractile vacuoles between the lobes of the chloroplast in the periphery of the cell. Charaeioehloris ascher, P which resembles a Charaeium, possesses numerous contractile vacuoles scattered in the cytoplasm. Charaeiosiphon,lyengar, another interesting genus, has two to five contractile vacuoles in each protoplasmic unit of a large coenocyte. Korshikov (1953) kept the coccoid forms with contractile vacuoles under a separate series,. the Vacuolales, under his Protococcineae, whereas others like Bourrelly (1958a, 1958b, 1959) and Fott (1959) included them under a separate order, the Tetrasporales. Contractile vacuoles also occur in the zoospores of a number of genera belonging to the Chlorococcaceae and Characiaceae, the zoospores of AeanthosPhaera,Polyedriopsis and in the amoeboid zoospores Qf Golenkinia and Marthea, the usual number being two. In Chlorococeum multi~ucleatum Starr, though nor!llally there are only two contractile _ vacuoles in the zoospore, occasionally the zoospore is larger and contains more than two vacuoles. Several contractile vacuoles (2-6) have also been reported in the zoospores and gametes of Charaeiosiphon Iyengar and in the egg of Dietyosphaerium indieumIyengar and Ramanathan. Non-contractile vacuoles may also be found in the protoplast of some of the Chlorococcales. Thus, in some species of Chloroeoeeum,.JikeC. vaeuolatum, the centl-al cytoplasm is vacuofate in actively growing cells. In the germlings of Charadosiphon,there are several vacuoles, but in the adult alga there is only a single large central vacuole filled with sap. The cytoplasm of Eremosphaerais peripheral with radiating strands towards the centre leaving several large vacuoles in between. Immature cells of Hydrodietyon, developed from zoospores, have innumerable minute va