276 AQUATIC PHYCOMYCETES 



rate, depending upon conditions in the medium. The fungus is of 

 particular interest because of the significance of the type of sporangial 

 discharge in relation to our present concept of genera. The situation 

 is evidently similar to that in Blastocladia pringsheimii (Sparrow, 

 1932b: 291), where a cap is often observed for a short time at the apex 

 of the mass of emerging zoospores but more often dissolves completely 

 before the swarmers are discharged. 



De Wildeman believes the species to be near Rhizophydium sphaero- 

 carpum. 



The wall of the egg was often stimulated to thicken around the 

 rhizoid of the parasite. The vegetative cells were not attacked, nor 

 was pollen of Alnus and Salix occurring in the water with the alga. 



Rhizophydium carpophilum (Zopf) Fischer 

 Rabenhorst. Kryptogamen-Fl., 1 (4): 95. 1892 



Rhizidium carpophilum Zopf, Nova Acta Acad. Leop. -Carol., 47: 200, pi. 

 20, figs. 8-16. 1884. 



Sporangia sessile, often clustered, at first spherical or ovoid, be- 

 coming somewhat pyriform after discharge, 9.6-25.2 \x in diameter, 

 wall thin, smooth, colorless; endobiotic part consisting of a tenuous 

 unbranched or sparingly branched rhizoid; zoospores two to forty 

 or more, spherical or slightly ellipsoidal, 3-6 (x in diameter, with a 

 colorless eccentric globule and a very long flagellum, emerging through 

 an apical fairly broad slightly elevated pore, movement swimming or 

 amoeboid; resting spore sessile, spherical, 5-9 [i. in diameter, with a 

 slightly thickened smooth wall and a large colorless oil globule, ger- 

 mination not observed. 



On oogonia and oosports of Saprolegnia sp., Achlya sp., etc., oc- 

 curring in clusters of one hundred or more on a single oogonium, 

 Zopf {be. cit.), isolated from soil, Remy (1948: 214), Reinboldt (1951 : 

 178), Germany; (?) on sporangium of Olpidiopsis saprolegniae, Sparrow 

 (1932b: 276, fig. lb), oogonia and oospores of Saprolegnia sp., Achlya 

 sp., oospores of Monoblepharis macrandra, Sparrow (1933c: 519), 

 Saprolegnia sp., Karling (1941a: 386), United States; oogonia of 

 Achlya racemosa, Tokunaga (1934b: 389, pi. 11, fig. 3), Japan; eggs 



