:V29 



HISTOKICAL EEVIEW OF THE FLOIUDE.E.— II. 

 By a. H. Chue€h, D.Sc. 



Taken at their simplest valuation as original autotrophic phyto- 

 benthon of the sea, and removed from all academic prejudices with 

 regard to an antithetic alternation of generations, which have obscured 

 the discussion of the origin of the vegetation of the land ^ — the 

 latter, so far as the Florideae are concerned, being considered as yet 

 non-existent, — this remarkable race expresses an independent line of 

 evolution in the sea from some ancestral stage of encysted plankton- 

 flagellate, attaining somatic and reproductive specialization along its 

 own lines, and meeting the problems of inevitable benthic wastage in 

 its own wa}'^, as a race apart from other residual marine phyla ; and 

 now narrowly circumscribed, but wholly intelligible by reference to 

 other benthic phyla also found in the sea, which had to meet the 

 same problems though with somewhat dilferent equipment. Haus- 

 torial connections and even nuclear migrations, which play so con- 

 spicuous a part in the nutrition of the carposporophyte, are but the 

 extension of the secondary pit-connections and nuclear migration 

 observed in somatic organization, though less obvious and more 

 minute ~ — again rendered possible by the special nature of the soft 

 gelatinous polysaccharides of the wall-membranes and the mechanism 

 of the primary ' Floridean-pit.' Coenocytic decadence of the trophocyte-^ 

 is paralleled by secondary coenocytic organization in the vegetative 

 soma of distinct generic types ^. Deterioration of the unilocular 

 sporangium, normally restricted to the production of one meiotic 

 tetrad ^ to a mere monosporangium ^, may be traced in PhseophyccEe, 

 though not becoming such a general feature " : while loss of phases 

 in the life-cycle (asexual, as in Kemalion, Scinaia, Lemanea, or 

 sexual, as in 'Rhodochorton, Rhodymenia 'palmata) is again but the 

 familiar indication of the deterioration induced by inferior and 

 limiting environment ^. 



The plants are no longer a group of mystery, but are readily 

 intelligible in all their domestic relations, though presenting a wide 

 range of variation in such processes, as also in somatic form and con- 

 sti-uction. The geneml working-plan of the life-cycle of the vast 

 majorit}' of the better-di:fferentiated types is based on a three-phase 

 system ; involving, that is to say, three successive individuals, or pre- 



1 Gf. Bower (1908), The Origin of a Land-Flora, p. 163. 



2 Oltmanns (1904), Algse, p. 602 : Rosenvinge (1888). 



"* ' Trophocyte,' the ultimate shapeless coenocytic fusion-mass of zygote and 

 parental plasma. 



■* Cf. Griffithsia, Gallithamnion sp., Bornetia, Mo)wsponi. 



' Gompsothamnion (jraciUiiaum according, to Buffham (1896. p. 189) produces 

 8 spores, Pleonosporium extends to 16-32. 



*" Monosporangia in many Ghantransia-lovma ; the ' monospore ' of Monospora 

 is multinucleate. 



' Phaeophycean monosporangia in Haplospora, Akinetospora : Oltmanns 

 (1904), loc. cit. p. 475. 



^ Gutleria, apogamous in the English Channel, is only represented by asexual 

 Aglazonia in Northern Seas : Rhodochorton is wholly a^^oxual in several species ; 

 most Gh antransia- fovms ; as also the fresh-water Tltorea. 



JOLENAL OF BOTAM-. VoL. 57. [DECEMliElt. lOlU.] 2 A 



