ABSTRACTAllochytridium luteumis a cellulolytic, monocentric chytrid. The incipient sporangium enlarges from the germ tube, and the sporangium has a single rhizoidal axis and single papilla or discharge tube mounted by a small operculum. The lipid globule in the zoospore is golden and the culture vivid yellow. Good sources of carbon in culture media are glucose, sucrose, lactose, cellobiose, galactose, starch, cellophane and xylan. Under certain conditions it can also utilize fructose and xylose. Good sources of nitrogen include tryptone, peptonized milk, urea, ammonium sulfate and sodium nitrate. Zoospores are very like those ofA. expandensexcept that the rumposome is two-and three-tiered.