CHYTRIDIALES 451 



P. parasiticus has also been reported in Europe in recent times by 

 Scherffel (op. cit.), who gave an extensive account of its morphology 

 and life history, and in the United States by Sparrow (1943); in both 

 places it occurred as a parasite of Tribonema bombycina. Polyphagus 

 nowakowskii Raciborski on Chlamydomonas, in Java, and P. ramosus 

 Jaag and Nipkow on Sphaerocystis, in Switzerland, have been recorded 

 only by their authors. 



It is difficult to draw definitive lines between the species. Raciborski's 

 fungus appears to differ from the others chiefly in forming smaller, 

 colorless zoospores. 



KEY TO THE SPECIES OF POLYPHAGUS 



Parasitic on Euglena and Chlamydomonas; resting-spore wall spiny or 

 smooth 

 Zoospores cylindrical, ellipsoid or ovoid; globule colored 



Prosporangium typically fusiform 01 clavate, occasionally globose; 

 sporangia distinctly elongate, zoospores with a pale-golden 

 globule; res'ing spore intercalary in the conjugation tube, 



wall spiny P. euglenae, p. 452 



Prosporangium typically globose; sporangia globose, ovoid or 

 curved, zoospore with a bluish-green globule; resting spore 

 terminal in the conjugation tube, wall smooth ...P. laevis, p. 453 



Zoospores spherical, globule colorless P. nowakowskii, p. 454 



Parasitic on filaments of Tribonema and on Sphaerocystis ; resting-spore 

 wall spiny 

 Parasitic on Tribonema ; zoospores spherical, 6-8 y. in diameter ; rest- 

 ing spore globose, 9-18 [j. in diameter P. parasiticus, p. 455 



Parasitic on the planktonic alga Sphaerocystis ; zoospores spherical, 

 4-5 tx in diameter; resting spore subglobose or ellipsoidal, 

 12-24 |jl long by 10-16 [i in diameter P. ramosus, p. 456 



gametangia. F-G. Polyphagus laevis Bartsch: F, small mature sporangium 

 produced from prosporangium resting between three parasitized cysts of 

 Euglena; G, very young thallus resting directly on Euglena. H-J . Polyphagus 

 parasiticus Nowakowski on Tribonema: H-I, young thalli lying between fila- 

 ments of host; /, mature resting spore. 



(A-B, Ingold, 1940; C-E, Serbinow, 1907; F-J, Sparrow, 1943) 



