CHYTRIDIALES 191 



Sorus sessile on the prosorus or formed at the tip of a discharge 

 tube, wall always divided into a varying number of seg- 

 ments, not surrounded by a common soral membrane at 

 maturity, simple or compound Micromyces, p. 192 



ENDODESMIDIUM Canter 



Trans. Brit. Mycol. Soc, 32: 72. 1949 



(Fig. 16 F-G, p. 196) 



"Thallus endobiotic, holocarpic, at first naked, later transformed 

 into a smooth-walled prosorus; sorus endobiotic, thin walled, smooth, 

 the content dividing into numerous bodies which emerge through pa- 

 pillae in the external medium or into the cavity of the host; sporangia 

 spherical producing minute zoospores; zoospores posteriorly uni- 

 flagellate with a conspicuous oil globule" (Canter, he. cit.). 



Parasites of desmids. 



In this genus the sporangia are usually liberated from the sorus as 

 sluggishly moving amoeboid or, occasionally, uniflagellate structures 

 which soon come to rest, encyst, and give rise to from two to five mi- 

 nute zoospores. The fate of these zoospores is unknown; probably 

 they reinfect desmids. It is, however, possible that they function as 

 gametes. See discussion under Micromyces, p. 193. 



Endodesmidium formosum Canter 

 Trans. Brit. Mycol. Soc, 32: 73, figs. 1-2, pi. 7, 8. 1949 



"Prosorus oval, 28.5 x 16.5 to 15.6 x 10.6 u,, with a smooth, usu- 

 ally purple wall; sorus subspherical, 16-25 u. high x 21-12 u, broad, 

 having at maturity two oppositely directed dehiscence papillae, the 

 content dividing into about fifty bodies (4 u. in diameter) with a con- 

 spicuous mass of oil and rarely a single, short posterior flagellum (6-8 \x 

 long), emerging through the papillae; sporangia spherical, 4 [i in diam- 

 eter, discharging two to five minute spherical zoospores 1 u, in diam- 

 eter, with a conspicuous oil globule and long posterior flagellum; 

 movement active swimming; resting spore similar to prosorus, wall 

 slightly thicker" (Canter, loc. cit.). 



Parasitic in Netrium oblongum, Cylindrocystis crassa, and C. bre- 

 bissonii, Great Britain. 



