The gymnocarpic development of the very small and gill-less fruit-body of Marasmius cornelii is directed by intrinsic factors until the lengthening stem becomes geotropic. The primordium is covered from a very early stage by a hymenioderm of clavate encrusted cells with a few lanceolate pileocystidia; the smooth clavate cells are a later development from the marginal growth of the pileus. The intercalary formation of the stem separates the pileus from the basal disc which acts as a turgid cushion supporting the stem round its insititious base. The hymenium is microscopically collariate. The Malayan M. poculiformis spec. nov. develops in the same way but lacks the basal disc to the stem which lengthens by secondary septation of its hyphae.