CHYTRIDIALES 421 



an endooperculum and apophysate sporangium. Its development when 

 lying free in the water is like that of Polyphagia. 



? Rhizidium variabile Canter 

 Trans. Brit. Mycol. Soc, 31 : 100, figs. 4, 5, pi. 10, figs. 4, 5, 6. 1947 



"Thallus monocentric, extramatrical part consisting of a sporangium 

 6-13 u. in diameter (developed from the encysted zoospore), and a single 

 stout rhizoid, which may have one or more swellings. Intramatrical 

 part sometimes swollen, tapering to a branched rhizoidal system. 

 Sporangium containing 1-20 zoospores which emerge, surrounded by 

 a vesicle, on deliquescence of the sporangial apex. Zoospores spherical 

 4.4-5 \i in diameter, with a single oil globule 1-2 \x in diameter, and a 

 posterior flagellum 26 \l long. Sporangium wall collapsing after dehis- 

 cence. Resting spores not observed" (Canter, loc. cit.). 



On dead Spirogyra sp., Great Britain. 



Both the description and figures of this species are strongly indicative 

 of abnormal development, probably due to lack of essential food 

 materials. This supposition seems borne out by the fact that the fungus 

 was found on Spirogyra which had so disintegrated as to be almost 

 unrecognizable. 



EXCLUDED SPECIES OF RHIZIDIUM 



* Rhizidium algaecolum Zopf, nom. nud. 1 



Nova Acta Acad. Leop.-Carol., 47: 204. 1884 



In manuscript, not connected with any figure or description. 

 On Spirogyra, Germany. 



* Rhizidium equitans Zopf, nom. nud. 



Pilzetiere oder Schleimpilze, p. 6. Breslau, 1885 



Inadequately described. Zopf later (1890) called this fungus 

 " Rhizophydium equitans" also a nomen nudum. 



1 Various names such as this one and combinations such as Rhizidium olla, R. 

 sphaerospermum, and Ewhizidium intestinum occur in Zopf's papers. These should 

 all be regarded as nomina inula. 



