1920] Setchell-Gardner: Chlorophyceae 275 



Order 5. SCIIIZOGONIALES west 



Thallus filamentous or membranaceous, deep green; cells dividing 

 in one, two or three planes strictly at right angles to one another, 

 chromatopiiores axile ; multiplication by proliferation (or gemmation) 

 of the thallus, by akinetes, or by the latter directly forming aplano- 

 spores ; zoospores and gametes unknown. 



West, G. S., Brit. Freshw. Algae, 1904, p. 98. 



This order differs from that of the Ulvales bj- the cells possessing 

 axile instead of parietal chromatophores, and by the absence of zoo- 

 spores and gametes. Otherwise, the members in general appearance 

 closely resemble those of the Ulvales. The order comprises one family 

 and one to four genera according to the views of different writers. 

 The species are largely inhabitants of fresh water or of damp, usually 

 foul, earth, but a few are marine. 



, FAMILY 10. SCHIZOGONIACEAE chodat 



The characteristics are the same as those of the order. 



Chodat, Alg. vertes de la Suisse, 1902, p. 341. 



In choosing the name of this family, all depends upon whether 

 Schizoganium is to be retained a.s a distinct genus. Until more 

 definite cultural work has been carried through, it seems best to us 

 to retain Schizogonium distinct from Prasiol-a and, consequently, we 

 have adopted Chodat 's name in preference to the Prasiolaceae of 

 West (1904) or the Blatosporaceae of Wille (1909). 



Key to the Genera 



1. Adult frond an expanded membrane 22. Prasiola (p. 275) 



1. Adult frond a solid filament 23. Gayella (p. 279) 



22. Prasiola Menegh. 



Frond membranaceous, monostromatic, attached by short filiform 

 prolongations, by the edge of the membrane, or by a thickened stipe; 

 cells with stellate, axile chromatophore and one pyrenoid, dividing 

 to form groups of fours, these groups forming similar larger groups, 

 the spaces between the groups of various orders constituting narrower 

 or wider spaces, running in definite directions through the frond ; 

 asexual reproduction, (1) by the breaking off of smaller portions 



