164 AQUATIC PHYCOMYCETES 



Three forms are distinguished: 



1. Forma major, tubes numerous, wall colored, 65-85 \l in diameter. 

 In roots of Thlaspi arvense, Belgium. 



2. Forma intermedia, tubes rather numerous, wall very slightly 

 colored and little thickened. 35-52 u. in diameter. In tissues of aquatic 

 plants. Switzerland. 



3. Forma minor, tubes less numerous, rather slender, wall very 

 slightly colored and little thickened, 1 7-26 \x in diameter. In tissues 

 of aquatic plants ("vegetable debris"), Switzerland. 



Because of the shape and ornamentation of the sporangium and 

 the central "spherule" with a more refractive portion in the contents, 

 these structures strongly resemble the oospores of an artotrogus type 

 of Pythium. 



? Pleotrachelus (?) rotatoriorum Scherffel 



Abstracts of Communications, V Inter. Bot. Congress, Cambridge, 1930: 222; 

 Arch. Protistenk., 73: 139, pi. 9, fig. 1. 1931 



Sporangium spherical to broad-oval, colorless, smooth- and thin- 

 walled, 44-55 [j. long by 51 u. wide, with three discharge tubes nearly 

 us long (4.4 u.) as wide (6.6 u.) and not extending beyond the host wall; 

 zoospores not observed. 



In egg of Anuraea cochlearis (?), Hungary. 



PLASMOPHAGUS de Wildeman 



Ann. Soc. Beige Micro. (Mem.), 19: 223. 1895 

 (Fig. 12 K, p. 124) 



Thallus endobiotic, causing hypertrophy (swelling and elongation) 

 of the host cell, plasmodial at first, later walled, holocarpic, without 

 rhizoids; sporangium inoperculate, nearly filling the host cell, its wall 

 distinct; /oospores posteriorly uniflagellate, with a single globule, 

 discharged individually through a pore formed at the tip of a single 

 short sessile (not projecting) papilla; resting spore not observed. 



Whether or not the genus is distinct from Olpidium is a matter for 

 further investigation. That the thallus nearly completely fills the host 

 cell, that it lacks a definite discharge tube, and that it causes hyper- 



