CHYTRIDIALES 281 



Rhizophydium eudorinae Hood 



Proc. Birmingham Nat. Hist, and Phil. Soc, 12:45, figs. 1-5. 1910; Trans. 

 Brit. Mycol. Soc, 5: 236, figs. 1-4. 1916 



Sporangium imbedded in the gelatinous sheath of the host colony, 

 sessile on the cell, broadly pyriform with a prolonged neck, the broad 

 apex extending slightly beyond the outer surface of the gelatinous 

 sheath, 20-35 \x high by 10-17 [i in diameter, wall thin, smooth, color- 

 less; rhizoid delicate and unbranched; zoospores numerous, ovoid, 

 2 u. in diameter, with a minute colorless eccentric globule and a single 

 flagellum, emerging from the apex of the sporangium in a compact 

 irregular mass imbedded in mucilaginous material from which, after 

 a period of rest, they escape; resting spore within the gelatinous sheath, 

 supported by a short stalk on the host cell, asexually formed, spherical, 

 10—16 (jl in diameter, with a thick dark rough wall, germination not 

 observed. 



Parasitic on the planktonic alga Eudorina elegans, Great Britain. 



The development of this species is similar to that of Phlyctidium 

 eudorinae. The zoospore comes to rest on the surface of the gelatinous 

 sheath of the host colony and produces a slender threadlike pene- 

 tration tube which pierces the sheath and becomes attached to the 

 nearest algal cell. Hood states that branches of the thread may pene- 

 trate two adjacent cells and that two zoospores may have one thread 

 in common. The latter statement seems very improbable. After at- 

 tachment to the algal cell the body of the zoospore enlarges and is 

 drawn gradually within the gelatinous sheath, so that often the mature 

 sporangium is sessile on the host cell, with its apex slightly protruding 

 from the sheath. The character of the rhizoid within the host cell is 

 not mentioned. From the description and the figures given, presumably 

 that part of the infection tube within the sheath expands and forms the 

 lateral walls of the sporangium. A somewhat similar type of develop- 

 ment is found in Dangeardia. 



Canter (1946: 134) believes this species is not valid, but represents 

 a mixture of Dangeardia mammillata and an epibiotic chytrid possibly 

 belonging to Rhizophydium or to Chytridium. 



