. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Fig. 255. Stipitococcus urceolatus W. &G. S. West. A—C, epiphytic on afilament of Mougeotia • D, epiphyticon Sphserozosma excavatum. A andD, x500; B and C, x 780. BotryococcacesB 405 Isogametes occur in Mischococcus, in which genus the zygospore ongermination divides in two directions in one plane, forming an epiphyticcushion, all the cells of which are situated on short, broad, mucilaginousstalks. This condition might almost be regarded as a
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Fig. 255. Stipitococcus urceolatus W. &G. S. West. A—C, epiphytic on afilament of Mougeotia • D, epiphyticon Sphserozosma excavatum. A andD, x500; B and C, x 780. BotryococcacesB 405 Isogametes occur in Mischococcus, in which genus the zygospore ongermination divides in two directions in one plane, forming an epiphyticcushion, all the cells of which are situated on short, broad, mucilaginousstalks. This condition might almost be regarded as a palmella-state. The genera are: Peroniella Gobi, 1887 ; Stipitococcus W. & G. S. West, 1898 ;Jfisikococcus Nageli, 1849 ; Chlorosaccus Luther, 1898 ; Racovitziella De Wildeman, 1900[ = Tetrasporopsis Lemmermann & Schinidle (according to Wille); DictyosphxropsisSchmidle, 1903]. Peroniella and Stipitococcus might be compared with Physocytium among the Palrnellacese,and similarly a comparison might be instituted between Mischococcus and Fig. 256. Mischococcus confervicola Nag. A, entire colony; B and C, parts of other x500. Family Botryococcaceae. It is highly probable that the Botryococcacese form a natural family andthe genera included in it seem to belong to the Heterokontse rather than tothe Isokontse. All the forms are colonial, the smallest colonies being those ofStichogloea and the largest those of Botryococcus. The colonies are, as a rule,free-floating and they may occur in great numbers in the freshwater Stichoglwa they usually consist of four or eight cells, enveloped in abundantbut rather indistinct mucilage, each group of four cells being disposed ina somewhat irregular cruciform manner, and the poles of the cells beingconnected by firmer and thicker mucilaginous strands. There are two parietalchromatophores in each cell. A less-known genus is Askenasyella in whichthe colonies, although larger than in Stichogloea, are
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