352 



Myxophycece 



Genus Chroococcus Nag., 1849. In this genus the cells are 

 globose or more or less angular, solitary or associated in simple 



families. They are free- 

 floating or mixed with 

 other blue-green Alga? to 

 form a stratum on wet 

 rocks. The integuments 

 are firm and often wide, 

 homogeneous or lamel- 

 lose, generally colourless, 

 but sometimes of a yellow- 

 ish-brown tint. The cell- 

 contents are granulose, of 

 a brilliant blue-green 

 colour, or more rarely 

 violet, olive-green, or 

 yellow-green. 



Fig. 166. A, Chroococcus giganteus West, 

 from Bowness, Westmoreland. B, Ch. turgidus 

 (Kiitz.) Nag., from Slieve Donard, Down, Ireland. 

 C and D, Ch. schizodermaticus West, from near 

 Windermere, Westmoreland. (All x 450.) 



Ch. turgidus (Kiitz.) Nag. 

 is the most widely distributed 

 species, often occurring in 

 quantity in Sphagnum-bogs ; diam. of cells 13 25 p; fig. 166 B. Ch. cohcerens 

 (Breb.) Nag., Ch. giganteus West (fig. 166 A), Ch. minor (Kiitz.) Nag. and 

 Ch. pallidus Nag. are not infrequent in ponds, lakes, and bog-pools. Ch. 

 schizodermaticus West (fig. 166 C and D) is remarkable for its tough lamellose 

 integuments, the layers of which are gradually split off and shed. Ch. lim- 

 neticus Lernm. is confined to the freshwater plankton. 



