SCYTONEMA. 235 



green, differing in intensity in different parts; here and 

 there gelatinous and semi-transparent. Filaments thick for 

 their length, very flexuous, with a pellucid colourless limb, 

 equal in breadth to the coloured, striated portion, which is of 

 a pale verdigris green." Grev. 



24. SCYTONEMA^. 



Char. " Branches increasing by the protrusion and division 

 of the central row of cells." Berk, in lit. 



Derivation. From CTKVTOS, a skin, and vrj^a, a thread; in 

 allusion to the toughness of the filaments. 



The genus Scytonema has hitherto evidently embraced the 

 description of plants belonging to two distinct genera. 



The above, therefore, is Mr. Berkeley's definition of the 

 genus Scytonema, as very properly proposed to be restricted 

 by that gentleman a considerable time ago. This concise de- 

 finition briefly describes the essential character of the altered 

 genus, but there are also others which serve to distinguish its 

 species from those which have hitherto been associated with 

 Scytonema, and which confirms the view adopted by Mr. 

 Berkeley of the necessity of forming two genera out of those 

 species. From the protrusion and division of the central 

 row of cells, it follows that the branches should frequently 

 be in pairs, and this is generally the case : the filaments, 

 also flaccid, of nearly equal diameter, are rarely moniliform. 

 The definition of the reconstructed genus Scytonema might 

 stand more fully thus : 



Char. Filaments^/facczW, of nearly equal diameter. Branches 

 usually in pairs, and formed by the protrusion and divi- 

 sion of the central row of cells. Cells generally quadran- 

 gular, rarely if ever regularly moniliform. 



Kiitzing, in his " Phycologia Generalis," has removed one 

 species from the genus Scytonema, S. ocellatum, and formed 

 for it a new genus Sirosyphon; but still the genus Scyto- 

 nema of Kiitzing does not in the most remote degree cor- 



