SUB-CLASS in. 



CHLOROSPERMEJ;, OR GREEN ALGM. 



Diagnosis. Plants almost always grass green ; rarely olivaceous, or lurid purple, still 

 more rarely red. Propagation either by simple cell-divisioti ; by the transformation of 

 the colouring matter of the cells of the whole frond, or of some of the cells, into zoospores; 

 or rarely by ordinary spores developed in proper spore-cases. Antheridia, containing 

 spermatozoids, have been observed in some. Marine, or living in fresh-water streams, 

 ponds, and ditches, or in damp situations. 



It is difficult, in a few words, to give such a diagnostic character of the Algae 

 included in this sub-class as shall comprise all the exceptional cases. The general idea 

 of the group is that it shall contain Algae of a herbaceous or grass green colour, propa- 

 gated by zoospores, or by the transformation of some considerable portion of the whole 

 of the endochrome into spores, without these spores being developed within proper spore- 

 cases, distinct from the ordinary cells of the frond. In the great majority of these 

 plants both characters are found ; but some few genera and species which agree with 

 the rest in the dispersed fructification, or in being propagated by zoospores, are of a 

 purple or red colour, thereby approaching the Rhodosperms in appearance ; while others 

 are olivaceous, and thus seem to approach the Melanosperms. It does not appear 

 to be desirable, for the mere variation in colour, to separate plants which are 

 in other respects so closely allied as are the Porphyrce to the Ulvce, or the red 

 Palmellacea; to those of a green colour. It would be necessary, were we to remove 

 these aberrant genera and species to the Rhodosperms, to construct special Orders 

 to receive them, nor could we place these new Orders in the series of Orders 

 as at present constructed ; but must establish for them a new division of the 

 sub-class, which would be characterised by the absence of cystocarpic fruit and of 

 tetraspores ; that is to say, by the absence of the fructification common to the whole of 

 this sub-class. Thus it would appear that these purpurascent Algse are more removed 

 from true Rhodosperms, notwithstanding the red colour of their spores, than from 

 Chlorosperms ; and consequently we retain them in this division. A graver anomaly, 

 as it appears to me, occurs in the genera which produce spores of the ordinary character 

 (not zoospores) contained within proper cysts. These have been removed by Endlicher 

 and others to the Melanospermic sub-class ; and certainly they show a considerable 

 approach to that group. But on the other hand, in the characters of their vegetation, 

 in the structure, habit, colour, and general aspect of the frond they are so closely united 

 to true Chlorosperms, that I am unwilling to separate them ; particularly as they do not 

 seem to be equally nearly related to true Melanospermese. These exceptional genera were 

 formerly included in SiphonecB,a.n(iwi:& in this work separated under the name Dasycladece. 



B 



