1^--^] SetcheU-Gardner: Melanophyceae 539 



26. Colpomenia Derb. and Sol. 



Frond solid in the juvenile stage soon becoming hollow, rather thin 

 and membranaceous, whole when young, becoming irregularly, more 

 or less lacerated in age, consisting of two tissues, an inner tissue of 

 large, rounded, nearly colorless, thin-walled cells and a cortical tissue 

 of small, more or less cuboidal, assimilating cells; plurilocular game- 

 tangia in early stage of development growing around groups of hair 

 filaments, later spreading over the entire surface of the frond ; para- 

 physes (?) unicellular, clavate, scattered. 



Derbes and Solier, Mem. phys. alg., 1856, p. 11. 



This is the third genus among the Scytosiphonaceae to show a mul- 

 titude of variations without sharp distinctions and no less than five 

 forms, varieties, or species have been described and named. The type 

 of the genus is conceived of as nearly a globular plant, thin-walled and 

 while, at times, slightly bullose, at least neither thick-walled nor pro- 

 vided with conspicuously projecting, wart-like or finger-shaped lobes. 

 Nevertheless, such variations occur, especially on our coast, where the 

 variation within the genus seems to have reached its maximum. We 

 have placed all of these species, varieties, and forms under one species, 

 with a series of varieties, much as we have done in the case of Scyto- 

 siphon and Ilea, but these variations, being more pronounced, have 

 been segregated into varieties and forms rather than into forms and 

 subforms. Nevertheless they may be simply environmental effects or 

 "ecads." 



Colpomenia sinuosa (Roth) Derb. and Sol. 



Plate 45, figs. 82-86 



Frond sessile, attached by a broad base, thin and membranaceous, 

 4-10 cm. diam., filled with water when young, later collapsed and 

 somewhat complanate, spherical to irregular in form, 0.25-0.35 mm. 

 thick ; color dark brown ; cortical layer of cells consisting of 1-2 rows 

 of cuboidal or polygonal cells, the inner layer of 2-5 rows of larger, 

 more or less rounded cells; plurilocular gametangia 18-22/* long, 5-8/* 

 broad, the loculi frequently in two rows. 



Growing on rocks and on other algae in the middle and lower 

 littoral belts. Common along the whole Pacific coast, from Yakutat 

 Bay, Alaska, to southern California. 



