A Contribution to the Life History and Geographic Distribution of the Genus Allomyces

Abstract

Almost thirty years ago Butler (1911) discovered in India a peculiar aquatic fungus to which he gave the name Allomzyces arbuscula. This organism is a member of the phycomycetous order Blastocladiales, and possesses two distinct types of sporangia; thin walled zo6sporangia, liberating posteriorly uniciliate zo6spores, and thick walled or resistant sporangia, which, after a period of dormancy, release zoospores similar in all respects to those from the zo6sporangia. It remained for Kniep (1929) to describe from Java a second species, A. jazanicus, which, while having zo6sporangia and resistant sporangia as in A. arbuscula, also produced paired gametangia liberating male and female gametes structurally similar to the zoospores except in size. In the next year, Kniep (1930) discovered that the gametangia were not produced on the same mycelium as were the two kinds of sporangia; in fact, the life cycle of A. javanlicus was shown to be characterized by an alternation of generations. The male and female gametangia produced on the sexual mycelium were observed to liberate gametes which fuse to form a motile biciliate zygote, which in turn develops into an asexual mycelium. On the asexual mycelium are borne the thin walled zo6sporangia, whose zoospores form new asexual plants, and thick walled or resistant sporangia, germinating to produce zo6spores which develop into sexual plants. A subsequent reexamination of A. arbuscila by Hatch (1933, 1935) disclosed a life cycle identical with that of A. javanicus. The distinction between the two species rests, however, on the arrangement