BotryococcacesB 



405 



Isogametes occur in Mischococcus, in which genus the zygospore on 

 germination divides in two directions in one plane, forming an epiphytic 

 cushion, all the cells of which are situated on short, broad, mucilaginous 

 stalks. This condition might almost be regarded as a palmella-state. 



The genera are : Peroniella Gobi, 1887 ; Stipitococcus W. & G. S. West, 1898 ; 

 Jfisi'kococcus Nageli, 1849 ; Chlorosaccus Luther, 1898 ; Racovitziella De Wildeman, 1900 

 [ = Tetrasporopsis Lemmermann & Schinidle (according to Wille) ; Dictyosphxropsis 

 Schmidle, 1903]. 



Peroniella and Stipitococcus might be compared with Physocytium among the Palrnellacese, 

 and similarly a comparison might be instituted between Mischococcus and Prasinocladus. 



Fig. 256. Mischococcus confervicola Nag. A, entire colony; B and C, parts of other colonies. 

 All x500. 



Family Botryococcaceae. 



It is highly probable that the Botryococcacese form a natural family and 

 the genera included in it seem to belong to the Heterokontse rather than to 

 the Isokontse. All the forms are colonial, the smallest colonies being those of 

 Stichogloea and the largest those of Botryococcus. The colonies are, as a rule, 

 free-floating and they may occur in great numbers in the freshwater plankton. 

 In Stichoglwa they usually consist of four or eight cells, enveloped in abundant 

 but rather indistinct mucilage, each group of four cells being disposed in 

 a somewhat irregular cruciform manner, and the poles of the cells being 

 connected by firmer and thicker mucilaginous strands. There are two parietal 

 chromatophores in each cell. A less-known genus is Askenasyella in which 

 the colonies, although larger than in Stichogloea, are still comparatively small. 

 The cells are rounded or pear-shaped and arranged in a more or less radiating 

 manner in the enveloping mucus. In each cell there is a single greatly 

 hollowed chromatophore. 



