The karyological phenomena in many Hymenomycetes have already been reported (OLIVE 1953) but investigations of this nature in India are so far very few (BosE 1937, BANERJEE et al. 1955, 1956, 1957, 1960, 1961). It is, therefore, worthwhile to study the karyological conditions in the life-cycle of Flammula dilepis B. & Br., a brown-spored member of the family Agaricaceae of which nothing so far is known as to its nuclear behaviour.