CHYTRIDIALES 279 



form, sometimes somewhat angular and blunt-cornered, usually not 

 over 10-15 \l in diameter, often having a narrow conical base, with a 

 small nearly sessile or slightly protruding apical papilla, wall color- 

 less, smooth, delicate, collapsing and disintegrating after spore dis- 

 charge; rhizoids richly branched, arising from the tip of a single stalk 

 which passes through the gelatinous sheath of the host; zoospores 

 not over fifty, spherical, with a single slightly eccentric colorless globule 

 and occasionally from one to two smaller ones, fiagellum delicate, 

 movement quick, in zigzag lines, or amoeboid; resting spore not ob- 

 served. 



Parasitic on Chroococcus turgidus, causing an epidemic both in the 

 field and in gross culture that destroys up to 75 per cent of the indi- 

 viduals, Zopf (be. cit.), Germany; Serbinow (1907: 159, pi. 4, figs. 

 35-36), Russia. 



The parasite caused a swelling of the gelatinous sheath and a quick 

 discoloration of the cell contents. The latter became olive green, then 

 dirty yellow brown. 



Serbinow noted that the fungus was a facultative parasite or even 

 a true saprophyte. The sporangia figured by him are more regularly 

 pyriform than those in Zopf's organism, and the rhizoid is an appar- 

 ently unbranched slender thread. In these characters it approaches 

 Rhizophydium simplex (Dang.) Fischer. 



Rhizophydium acuforme (Zopf) Fischer 



Rabenhorst. Kryptogamen-Fl., 1 (4): 93. 1892 



Rhizidium acuforme Zopf, Nova Acta Acad. Leop.-Carol., 47: 209, pi. 21, 

 figs. 33-44. 1884. 



Sporangium sessile, broadly pyriform, 6-16 [j. in diameter, with a 

 single apical papilla, wall thin, smooth, colorless; rhizoids delicate, 

 sparingly branched, arising from a main axis; zoospores about 2-2.5 \x 

 in diameter, with a single colorless globule, escaping through an apical 

 pore formed upon the deliquescence of the papilla; resting spore 

 sessile, spherical, generally smaller than the sporangium, with a smooth 

 thickened wall, the contents bearing a large globule, rhizoids delicate, 

 sparingly branched, arising from a main axis, germination not observed. 



