CHYTRIDIALES 431 



RH1ZOCLOSMATIUM H. E. Petersen 



Journ. de Botanique, 17: 216. 1903 

 (Fig. 27 G-I, p. 428) 



Mature thallus monocentric, eucarpic, consisting of a sporangial 

 rudiment (body of the encysted zoospore), apophysis, and delicate 

 rhizoids; sporangium inoperculate, formed from the sporangial rudi- 

 ment; zoospores posteriorly uniflagellate, with a single globule, formed 

 in the sporangium, emerging in an evanescent vesicle to undergo a 

 period of collective swarming before escaping, discharge pore basal, or 

 rarely subapical or apical; resting spore borne like the sporangium on 

 the rhizoidal system, thick-walled, sexually formed after conjugation of 

 thalli by means of rhizoidal anastomosis, germination not observed; 

 contributing thallus remaining small and rudimentary. 



The species thus far described are known as saprophytes in insect 

 exuviae and parasites of marine green algae. 



KEY TO THE SPECIES OF RHIZOCLOSMATIUM 



In insect exuviae in fresh water 



Globule of zoospore colorless R- globosum, p. 431 



Globule of zoospore rusty-orange R. aurantiacum, p. 432 



In the marine alga Codium fragile R. marinum, p. 433 



Rhizoclosmatium globosum H. E. Petersen 

 Journ. de Botanique, 17: 216, figs. 1-2. 1903 

 (Fig. 27 H-I, p. 428) 

 Sporangium spherical or subspherical, 9-22 \x in diameter (or larger), 

 wall slightly thickened, smooth, colorless; rhizoids extensive, delicate, 

 much branched, arising from a transverse broadly fusiform (5 u. broad 

 by 3 u. high), occasionally subspherical, pyramidal, or clavate apophysis ; 

 zoospores spherical, ovoid, or ellipsoidal, 3-4 \i long by 2-3 u. in diam- 

 eter, with a colorless centric or eccentric globule and a flagellum about 

 20 [x long, movement darting; resting spore borne like the sporangium, 

 subspherical, 8-14 \x high by 1 1-20 \x in diameter, with a smooth faintly 

 brown wall about 2 \x thick, contents with globules, germination not 

 observed; contributing thalli from one to two, spherical, 4-6 \x in diam- 

 eter, with a poorly developed rhizoidal system. 



