Aphanomyces parasiticus Coker 1923

Aphanomyces parasiticus Coker, Saproleg. 165. 1923
Hyphae parasitic on vegetative threads, young sporangia, and young oogonia of species of Achlya (A.flagellata, A. Orion, sterile Achlya, No. 1 of August 13, 1921), not attacking gemmae or eggs; vegetative hyphae endophytic at first, traversing host-threads from base to tip, growing out through walls of host only after exhausting the contents; threads of parasite 3-5.5 p thick, most about 4 p, straight and even at first, becoming somewhat swollen in places and distorted with age; sporangia usually formed outside the host, the spores emerging, later swimming normally for the genus ; sporangia not rarely forming inside the host, the spores not emerging, but encysting within the sporangium; spores 7.4—11 p thick; oogonia usually borne within the host-thread, not rarely without it, on short, lateral, inconspicuous branches, 14-22 p in diameter, not including the spines; wall warted to strongly spiny, the spines rarely up to 3 p long; eggs single, eccentric, nearly filling the oogonium, 12.8-21.7 p thick; antheridial branches of diclinous origin, usually long; antheridia single, irregularly oval, 11 by 14 p, applied to the base of the oogonium, often obscuring the oogonial stalk, the contents emptying completely into the oogonium.
Type locality: Chapel Hill, North Carolina.
Habitat: Parasitic on Achlya.
Distribution: New York, Massachusetts, and North Carolina; also in Europe.