412 



PROTOPHYTA 



Each cell contains a nucleus and a vacuole ; the green protoplasmic 

 contents break up ultimately into zoospores of a very peculiar form, 

 conical, with two cilia attached to the nearly flat base, recalling those of 

 ^^^.-^ Hydrurus (p. 256). 



In Dictyosphcerium Nag.,. 

 which ought possibly to be 

 placed under the Ccenobieae, the 

 free-swimming colony is com- 

 posed of globular or kidney- 

 shaped green gonids connected 

 together by delicate threads of 

 mucilage. New colonies are 

 formed by repeated biparti- 



B ^^^^^^^^ A N tion of the gonids, which fre- 



FIG. w.~-Hapiosph*ra -viridis Schm. Globe ( x 80), quently exist for a time without 



any enclosing cell-wall. Mis- 



chococcus Nag. consists of minute globular gonids connected together 

 in an arborescent manner and enclosed in a hyaline envelope, the whole 

 colony attached to fresh-water algae. Borzi (Malpighia, 1888, p. 133) 

 describes also a palmelloid form of Mischococcus, the cells of which 

 give birth to megazoospores with only a single cilium. The dendroidal 

 form may spring either from these zoospores or directly from the 

 palmella- cells ; its cells also produce uniciliated swarm-spores, similar to 

 the zoospores but smaller. They are apparently zoogametes conjuga- 



FIG. 338. Dictyosphczrium rcniforme 

 Buln. (x 400). (After Cooke.) 



FIG. 339. Mischococcus confenncola Nag. 

 (X 4 oo). (After Cooke.) 



ting to produce a biciliated zoosperm. Botrydina Breb., found on 

 moist ground, trunks of trees, &c., is composed of a number of minute 

 gonids enclosed in a pear-shaped or globular hyaline envelope, as much 

 as o-i mm. in diameter, and resembling Aphanocapsa among the 

 Chroococcaceae. It may possibly be allied to Botrydium. 



Chararium A. Br. is a minute green organism attached by a gela- 

 tinous stalk to algae or other fresh-water plants, often in groups. It is 



