CHYTRIDIALES 485 



phase diploid in nature (Sparrow, 1940a). Reduction division would 

 then occur upon the germination of the resting spore. There is, as yet, 

 no evidence to confirm this hypothesis. 



The remarkable ephemeral epibiotic sporangia characteristic of this 

 genus were apparently originally observed by Schroeter (1883) in 

 Physoderma (Urophlyctis) pulposa. The zoospores from these sporangia 

 at first formed on the young host plants new epibiotic sporangia with 

 a short bushy endobiotic rhizoidal system. Later the zoospores formed 

 germ tubes which penetrated the host and produced resting spore 

 plants. The existence of the epibiotic stage was confirmed by Biisgen 

 (1887) in P. butomi and then by Clinton (1902) in P. maculare, by 

 Sparrow (1934a; 1940a; 1946; 1947a) in P.menyanthis and P.maydis, 

 by Thirumalacher and Whitehead (1951) in P. aeschynomenis, by Couch 

 (1953) in P. maydis, by R. M. Johns (1957) in P. dulichii, and by 

 Sparrow (1957b) in P. lycopi. 



Physoderma marsiliae Brewster 1 

 Mycologia, 44: 99, fig. 1. 1952 

 Parasitic on Marsilea mucronata, United States. 



Physoderma aeschynomenis Thirumalachar and Whitehead 

 Mycologia, 43: 435, figs. 1-17. 1951 

 On the stems and rachis of Aeschynomene indica, India 



Physoderma aponogetonis Sparrow 



Trans. Brit. Mycol. Soc, 36: 348, fig. 1. 1953 



Parasitic on leaves and petioles of Aponogeton undulatus, Great 

 Britain (on material recently imported from Ceylon). 



Physoderma dulichii Johns 

 Mycologia, 49 : 298. 1957 

 On Dulichium arundinaceum. 



1 Species published since Karling (1950). 



