Aphanomyces stellatus

Aphanomyces stellatus De Bary, Jahrb. Wiss. Bot. 2:
178. 1859.
Hyphae straight, delicate, little branched, about 5.5-6.5 n in diameter, springing abundantly from the substratum, the tips rounded; sporangia produced from unchanged hyphae, very long, usually reaching to substratum; spores when in sporangium irregularly rod-shaped with uneven ends, on escape becoming rounded and encysting in an irregular group at the mouth of the sporangium, 8-8.5 m in diameter (at times a few larger double ones 11-12 p in diameter mixed with others), large cysts giving rise to two spores of normal size (according to de Bary, and confirmed by us); oogonia subspheric, borne on rather long or short lateral branches, normally covered more or less densely with conspicuous blunt tubercles or papillae up to 5.5 m long, the diameter of the oogonia, including papillae, about 22-33 m, the walls rather thin, unpitted, the cavity extending into the papillae; eggs about 16-26 p. thick, most about 18.5 p, single (rarely two, according to de Bary), the contents eccentric when fully mature, with an inconspicuous lunate series of droplets on one side in optical section; antheridial branches androgynous or also from neighboring threads, often branched; antheridia short-tuberiform, large, present on all or nearly all oogonia; fertilization uncertain.
Type locality: Germany.
Habitat: Fresh water and soil; parasitic on Achlya.
Distribution: North Carolina; also in Europe and Japan.