CHYTRIDIALES 165 



trophy of the infected cell are all characteristics exhibited by one or 

 another undoubted species of Olpidium. In these respects Plasmophagus 

 also resembles species of Rozella. However, it differs from Rozella 

 in that the walls of host and parasite are distinct, not fused. 



Plasmophagus oedogoniorum de Wildeman 

 Ann. Soc. Beige Micro. (Mem.), 19: 223, pi. 8, figs. 1-9, pi. 9, figs. 1-9. 1895 



Sporangium saclike and somewhat irregular, almost completely fill- 

 ing the swollen and elongated algal cell, 20-23 jjl long by 8-1 1 \i 

 broad (in Tribonema), wall thin, smooth, colorless, discharge papilla 

 lateral, small, just penetrating the host wall; zoospores ovoid or obo- 

 void, 3 u. long by 2 \i wide, with a colorless eccentric globule and a 

 flagellum; resting spore not observed. 



Parasitic in filaments of Oedogonium sp., de Wildeman (Joe. cit.), 

 France; Tribonema bombycina, Sparrow (1933c: 513, fig. I, 1), United 

 States. 



No measurements are given by de Wildeman and those contained 

 in the description above refer to the organism in Tribonema. It is prob- 

 able that the parasite of Oedogonium attained larger dimensions, but 

 this is only conjecture. 



ROZELLA Cornu 



Ann. Sci. Nat. Bot.. V, 15: 148. 1872 



Figs. 12 F-I, p. 124; Fig. 14, p. 179) 



Rozia Cornu, Bull. Soc. Bot. France, 19: 71. 1872. Non Rozea Besche- 



relle, Mem. Soc. Nationale Sci. Nat. Cherbourg, 16: 241. 1871-72. 

 Pleolpidium Fischer, Rabenhorst. Kryptogamen-Fl., 1 (4): 43. 1892. 



Thallus endobiotic, holocarpic, at first naked and indistinguishable 

 from the host contents, later walled, at maturity forming either the 

 rudiment of the sporangium, the wall of which is fused with that of 

 the hypertrophied host (except when intercalary), or the resting spore; 

 sporangium inoperculate, thin-walled, smooth, with one or more dis- 

 charge papillae; zoospores formed in the sporangium, posteriorly 

 uniflagellate, often with a single globule; resting spore endobiotic, 

 thick-walled, smooth or spiny, apparently asexually formed, lying 



