CHYTRIDIALES 255 



the mature resting spores. Germination unknown "(Canter, loc. cit.). 



Parasitic on the planktonic diatom Asterionella formosa, Great 

 Britain. 



Canter notes that this species is almost always present if the host 

 is. She says, however, that the greater part of the year its frequency 

 is too low to appreciably affect the number of Asterionella cells. At 

 certain times, particularly in autumn and winter, the Rhizophydium 

 multiplies rapidly to epidemic proportions (see p. 107). 



Canter and Lund (1951) suggest that Rhizophydium plank tonicum 

 may be an aggregate species. They believe the fungus described and 

 figured by Huber-Pestalozzi (1946:94, fig. 5 a-c) on Asterionella for- 

 mosa from Swiss plankton is not identical with R. planktonicum, 

 because of the presence of a swelling on the terminus of the rhizoid 

 in the Swiss form. 



Rhizophydium marshallense Sparrow 

 Mycologia, 40: 450, figs. 13, 15-17. 1948 



Sporangium sessile, spherical, 10-12 u, in diameter, colorless, smooth- 

 walled; endobiotic part consisting of a slender, at least once-branched, 

 rhizoid; zoospores somewhat ovoid, 2 \i or less in diameter, each with 

 a single hyaline, minute refractive globule and a posterior flagellum, 

 escaping through a minute variously placed pore; resting spore spheri- 

 cal, 10-1 5 (jl in diameter, faintly golden and densely covered with prom- 

 inent knoblike bullations, endobiotic part like that of the sporangium; 

 germination not observed. 



Parasitic on thalli and sporangia of Rhizophlyctis spp., Eleugelab 

 Island, Einwetok Atoll, and Rongelap Island, Rongelap Atoll, 

 Marshall Islands. 



How this, as well as several other species found on these remote 

 atolls, got there and survived in the nearly pure coral sands is an in- 

 teresting problem in distribution. 



Rhizophydium sphaerocystidis Canter 

 Ann. Bot. London (N.S.), 14: 280, fig. 10. 1950 

 "Thallus consisting of a sporangium sessile on the outside of the 



