CHYTRIDIALES 263 



Clustered on filaments of Mougeotia sp., Oedogonium vesication, 

 O. undulatum, Braun (loc. cit.), Germany; on various algae, Spirogyra, 

 Cladophora, Sorokin (1874b: 6, pi. 1, figs. 6-11, and loc. cit.), European 

 Russia; Oedogonium crassuscidwn var. idiosporum, W. R. I. Cook 

 (1932a: 135, figs. 7-12), Great Britain; Oedogonium sp., Atkinson 

 (1909a: 338), O. crenulato-costatum, O. plagiostomum, Mougeotia sp., 

 Graff (1928: 159), United States; Oedogonium sp., Litvinow (1953: 

 80), Latvia; pine pollen, Gaertner (1954b: 21), Equatorial East 

 Africa, South Africa. 



Braun considered the species a very doubtful member of the chy- 

 trids. This view has been shared by Petersen (1910: 551, footnote), 

 who believes the form should be entirely excluded from the chytrids 

 and placed in the Infusoria. As has been pointed out by Graff (loc. 

 cit.), Petersen gives no reasons for this change. It is possible that 

 Petersen is correct insofar as the form observed by Braun himself 

 is concerned. The curious production of a delicate, scarcely visible, 

 tilted conical prolongation of the discharge tube is not found on any 

 other chytrid, and the general resemblance of Braun's figures to the 

 immature stages of certain sessile choanoflagellates is very marked. 

 Since the name has been applied by later investigators to what is 

 unquestionably a chytrid, however, and since figures of spore dis- 

 charge have been shown (see especially Sorokin, 1874b), it is probably 

 best to retain Braun's species name. 



Rhizophydium rostellatum (de Wild.) Fischer 



Rabenhorst. Kryptogamen-Fl., 1 (4): 105. 1892 



Chytridium rostellatum de Wildeman, Ann. Soc. Beige Micro. (Mem.), 

 14: 19, fig. 6, 1890. 



Sporangium sessile, ovoid, with a single subapical beaklike pro- 

 longation or, more often, with two opposite diverging ones, wall thin, 

 smooth, colorless; rhizoidal system delicate, branched, arising from a 

 short thin main axis; zoospores spherical, with a large globule, escaping 

 through a pore formed at the tip of each beak of the sporangium; 

 resting spore not observed. 



On Spirogyra crassa, Belgium. 



