A phylum of microscopic fungi, the chytrids, that live in soil or fresh water. The body (thallus) is unicellular or a coenocyte and gives rise to threadlike hyphae or rhizoids; some species form a branching network (mycelium). The cell walls contain chitin, and some also have cellulose. Chytrids feed by secreting enzymes to digest material extracellularly in order to absorb the nutrients. They produce motile stages (zoospores) equipped with a single flagellum. Sexual reproduction is the norm; fusion of the gametes results in a zygote, which either produces motile zoospores or germinates directly into a new thallus.