302 AQUATIC PHYCOMYCETES 



that even if a rhizoidal system were definitely shown not to be present 

 in the dense host plasma he could not consider it a species of Olpidium 

 since the discharge tube does not penetrate the host wall. Further 

 observations, particularly on stained material, will be necessary before 

 this fungus can without doubt be referred to Olpidium, Khizophydium, 

 or, possibly, to Entophlyctis. 



Braun (1856a) records the remarkable fact that the zoospores of 

 the species which remained in the sporangium swarmed for as much 

 as 108 hours. Sorokin (loc. cit.) describes them as being actively motile 

 after 48 hours. 



? Rhizophydium digitatum Scherffel 

 Arch. Protistenk., 54: 223, pi. 10, figs. 103-104. 1926 



Sporangium single, somewhat broadly ovoid, with truncate apex, 

 8 [x in diameter, wall thin, smooth, colorless, bearing on the rim of 

 the flattened top five coarse, hollow, thin-walled sharp, somewhat in- 

 curved teeth 4 [A long by 2 \x thick; rhizoid broad, somewhat swollen 

 at place of attachment to the rounded base of the sporangium, thin- 

 walled, prolonged into a coarse filament which penetrates the host 

 cytoplasm, where it probably branches; zoospores and resting spores 

 unknown. 



On Gloeocystis, Mougeotia sp., Scherffel {he. cit.), Hungary. Zyg- 

 nema sp., Linder (1947:243, pi. 13, fig. G) (F. slide No. 2704), 

 Canadian Eastern Arctic. 



A form with four teeth, incompletely observed by Sparrow (1933c: 

 529, fig. I, 17), may be referable to this species. 



? Rhizophydium dubium de Wildeman 

 Ann. Soc. Beige Micro. (Mem.), 19: 113, pi. 3, figs. 26-28. 1895 

 Sporangium sessile, spherical, with a protruding apical papilla, wall 

 thin, smooth, colorless; rhizoids branched, delicate, arising from a 

 short central axis; zoospores not observed, apparently emerging through 

 a wide pore formed upon the deliquescence of the papilla; resting 

 spore not observed. 



On filaments of Spirogyra, France. 



