CHYTRIDIALES Ml 



The latter is not sessile on this apophysis but separated from it by a 

 short length of unexpanded rhizoidal axis. At spore discharge, the 

 sporangium wall swells and thickens and its substance, including the 

 spines, slowly dissolves. Coincidently, the spores become active and 

 swim away. Only an irregular collar of sporangium wall persists at the 

 base. 



Solutoparies PYTHH Whiffen 



Mycologia, 34: 543, figs. 1-27. 1942 



"Thallus parasitic. Sporangia ovoid to spherical, 14.3 y. x 16.4 [i to 

 68.4 y. X 80.3 y.; wall spiny, spines conical, up to 5 [j. in length. Rhi- 

 zoidal system cut off by cross wall from mature sporangium, tips of 

 rhizoidal branches adhering to but not penetrating host hyphae. Dis- 

 solution of sporangial wall complete except for basal portion, freeing 

 the spore mass, enclosed in a gelatinous matrix; zoospores separating 

 as surrounding matrix dissolves, swimming away singly. Zoospores 

 spherical, 4.5 y. to 5.6 (jl, hyaline with single colorless oil globule. Resting 

 spores unknown" (Whiffen, be. cit.). 



Exoparasite of Pythium sp.. United States. 



Although the tips of the rhizoids were not observed to penetrate the 

 host hypha but, rather, to wrap around it, wherever they made contact 

 the host was stimulated to abnormal branching. These complexes of 

 hyphae favored development of the parasite, since more hyphal ele- 

 ments of the host were made available in its immediate vicinity. 



OBELIDIUM Nowakowski 



Cohn, Beitr. Biol. Pflanzen, 2: 86. 1876 



(Fig. 27 A-E, p. 428) 



Mature thallus monocentric, eucarpic, consisting of a sporangial 

 rudiment (the body of the encysted zoospore) which is differentiated 

 into an apical solid mucro, a central thin-walled expanded sporogenous 

 region, and a thick-walled cuplike or stalklike basal part resting on an 

 apophysis from which radiate the main axes of the rhizoidal system; 

 sporangium inoperculate, formed from the sporangial rudiment; zoo- 

 spores posteriorly uniflagellate, with a single globule, formed in the 

 sporangium, emerging through a lateral pore and undergoing a period 



