Feisri-arv, 1912. 



KNOWLEDGE. 



73 



The Flagellates included by Pascher under the family 

 Cryptomonadinae are rather few, the most interesting (in 

 addition to the two new genera just mentioned) being Zooxan- 

 thcUa which lives in symbiosis with lowly animals like the 

 Radiolaria. The Crj-ptomonads are distinguished from the 

 other Flagellates, especially the Chrysomonads. by the 

 remarkabK- dorsiventral or one-sided (as opposed to radial) 

 symmetry of the body, which is obliquely truncated at the 

 anterior end : the presence of a curious furrow, which is 

 usually in the longitudinal plane but in Protochrysis is 

 e(|uatorial: the frequently red or blue tinge of the usually 

 brown chroinatophores ; the unequal pair of cilia inserted in 

 the furrow. 



Starting from the simple Chrysomonads, these probably gave 

 rise to the Cryptomonads. and the red and blue varieties of 

 I he latter then became fixed characters in the red genus 

 Rlioiloiiioiias. which may be regarded as the direct Flagellate 

 .incestor of the Red .\lgae, and in the blue-green genera 

 CItrodiiioiias and Cyanomonas, which may have given rise 

 to the Blue-green Algae. A third line arising from the 

 Cryptomonad group (t-.^.. Cryptochrysis and Protochrysis) 

 passed through Cryptomonas, in which the apical furrow 

 L;radually becomes deeper and forms an " oesophagus " (a 

 ■ .ivity which extends more or less deeply into the protoplast, 

 lud into which the contractile vacuole opens) ; this line of 

 l.irger and more highly organised forms ends blindly in 

 heterotrophic (saprophytic) genera like Chiloiiwnas and 

 Cyatlwutoiias. 



The most important line arising from the Cryptomonads, 

 however, is that leading through the remarkable series of 

 I'haeocapsaceae to the higher Brown Algae. The 

 I'haeocapsaceae correspond, in the Brown Series, to the 

 I'etrasporaceae in the Green Series leading from Green 

 I'lagellatcs to Green Algae. In the Phaeocapsaceae we get a 

 series of forms passing almost insensibly from true Flagellates 

 to true though simple Brown Algae. The first known member 

 ill this series is Pliacoplax marina (formerly called 

 Pluicococcus inarinits). In Pliacoplax. the motile 

 reproductive cells exactly resemble Cryptochrysis, having 

 the same dorsiventral symmetry and the same minute 

 structure, but the plant passes the greater part of its 

 existence in the motionless condition, dividing to form a mass 

 of cells enveloped by mucilage derived from the cellulose walls 

 (the Cryptomonads themselves have no cellulose walls). 

 Through forms showing increasing suppression of the motile 

 phase, and increasing elaboration of the cell-masses formed 

 by division in the resting stage, we come to the genus 

 Phacothaiitiiion. which forms branch filaments and produces 

 sexual reproductive bodies (gametes) — sexual reproduction 

 does not occur in the Cryptomonads or any other Flagellates 

 so far as known. 



Pascher's paper is an interesting contribution to the evolu- 

 tion of the .-Mgae from Flagellates. The phylogeny of the 

 Green Algae has been worked out in great detail — see Black- 

 man's well-known paper yAnnals of Botany, 1900) — but less 

 is known concerning the relation of Brown Flagellates to 

 Brown .Mgae, and still less regarding the Red and Blue- 

 green Flagellates and Algae. Still, there seems to be little 

 ground for doubting that the Brown, Red, and Blue-green 

 .■\lgae have arisen from some such Flagellate group as the 

 Cryptomonads. 



CL.-\SSIFIC.\TION OF BRVOPHVTA.— At the end of a 

 series of papers on "The Inter-relationships of the Bryophyta" 

 in the A't-K' Phytologist, the present writer has proposed a 

 new classification of this group of plants. The old-established 

 primary division of the Bryophytes into Mosses and Liver- 

 worts is called in question, especially in connexion with the 

 small families .Anthocerotaceae and Sphagnaceae ( Peat Mosses), 

 and it is interesting to note that in certain of the characters 

 which have been regarded as ext;luding the .-Vuthoceros family 

 from Liverworts on one hand, and the Sphagna from the 

 Mosses on the other, these two aberrant groups show a strik- 

 ing resemblance to each other. After discussing the advisa- 

 bility of dividing the Bryophytes into four classes — true Liver- 



worts, Anthocerotes, Sphagna, and true Mosses — the writer 

 proceeds to elaborate a new classification. It is proposed to 

 divide the Bryophytes into ten independent groups, as 

 follows : — 



I. — Sphaerocarpales, including Sphaerocarpaceae (Sphacro- 

 carpus and Gcothallits) and Riellaceae (Rielta). 



II. — Marchantiales, including Ricciaceac, Corsiniaceae, 

 Targioniaccae, Monocleaceae, Cleveaceae, Aytoniaceae, and 

 Marchantiaceae. 



III. — Jungermanniales, including the Anacrogynous families 

 .Aneuraceae, BIyttiaceae, Codoniaceae; the transitional family 

 Calobryaceae ; and the .\crogynous families Lopho^iaceae, 

 Ccphaloziaceae, Ptilidiaceae, Scapaniaceae, Radulaceae, 

 Pleuroziaceae, Porellaceae, and Lejeuneaceae. 



IV. — Anthocerotales, including .Anthocerotaceae. 



V. — Sphagnales, including Sphagnaceae (Sphagnum). 



VI. — .-^ndreaeales, including Andreaeaceae (Andrcaea). 



VII. — Tetraphidales. including Tetraphidaceae. 



VIII. — Polytrichales, including Polytrichaceae and Dawson- 

 iaceae. 



LX. — Buxbaumiales, including Buxbaumiaceae and Diphys- 

 ciaceae. 



X. — Eu-Bryales, including all the higher mosses. 



.Ml these groups are characterised and their relationships 

 discussed. The arrangement of the lower Bryophytes is 

 based largely on the writer's own work, while for the higher 

 mosses (Eu-Bryales) the writer accepts the views of Lorch, 

 Philibert, and Fleischer, with some modifications. 



The classification of the higher mosses can no longer be 

 based upon such characters as the position of the fruit (the 

 old groups .\crocarpi and Pleurocarpi) nor upon the presence 

 or absence of a peristome (Stegocarpi and Cleistocarpi of 

 previous authors), though the various terms — acrocarpous, 

 pleurocarpous, stegocarpous, cleistocarpous— may be retained 

 for purely descriptive purposes. In the new classification of 

 mosses proposed by the writer, the Fn-Bryales are divided 

 first into Haplolepideae, Heterolepidcae, and Diplolepideae, 

 according to the single or double character of the peristome, 

 and the various cleistocarpous forms are simply distributed 

 through these groups according to what appear to be their 

 aftinities as either reduced or primitive types allied to difterent 

 peristome-bearing families. The further division of the great 

 group Diplolepideae is based upon minute, but readily 

 observable, differences in the structure of the peristome. 



Throughout this series of papers, it is assumed as a working 

 theory that the Bryophyta form an ascending series, marked 

 by progressive elaboration of the sporophyte ; that the 

 sporogoni'.nn of the Bryophyta has arisen as an interpolated 

 generation, with increasing " sterilisation of potentially 

 sporogenous tissue," from the segmented oospore : that although 

 the archaic condition in which the sporogonium was a simple 

 spore-fruit consisting of a mass of sporogenous cells, is not 

 actuallv realised in an\- known Bryophyte, we have in the 

 Ricciti capsule a primitive sporophyte in which sterilisation 

 has proceeded only as far as the formation of a single peri- 

 pheral cell-layer forming the capsule-wall ; and that the Riccia 

 type of sporogonium is not only the simplest but also the most 

 primitive known. 



This theorv has been much disputed, but at any rate the 

 question is apparently still an open one. The writer's object 

 in this series of papers has not been so much to discuss the 

 position of the Bryophvta as a whole and its relations to other 

 divisions of the Vegetable Kingdom, as to give a summary of 

 the various families of Mosses and Liverworts and of their 

 relations one to the other. 



The ■■ Inter- Relationships of the Bryophyta" is obtainable 

 separatelv. as a " ATetc' Phytologist Reprint.'' from the Editor 

 of theA'e'tc- P/j>7o/og;s^ Botany School. Cambridge University 

 (price 4 -, postage 4d.) ; it contains numerous illustrations and 

 full lists of the Uterature of Mosses and Liverworts. 



