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a class of lower fungi that usually have a well-developed multinuclear, noncellular mycelium. The class includes approximately 800 species. Reproduction occurs sexually by means of gametes; asexual reproduction occurs by means of motile spores formed within zoosporangia or by means of nonmotile spores that develop endogenously in sporangia and exogenously on distinctive conidiophores.
The Phycomycetes are divided into two subclasses, oomycetes and zygomycetes, according to their manner of reproduction. In modern taxonomy, the two subclasses are often designated as independent classes. Many of the Phycomycetes resemble green algae in their body structure and reproductive organs. However, it is possible that this is a superficial resemblance indicative of convergence, and that the ancestors of the phycomycetes were the fungi Archimycetes. Some mycologists consider Archimycetes and Phycomycetes to constitute a single class of lower fungi. Most of the Phycomycetes are aquatic saprophytes. More highly developed species have adapted to terrestrial existence, and some parasitize plants, animals, and humans.
M. A. LITVINOV