ABSTRACTMicrosorum alternifoliumis a threatened fern of the family Polypodiaceae. Present paper deals with the events of spore germination, gametophyte growth and differentiation, ontogeny of sex organs and development of sporophytes inin vitroconditions. Spore germination and prothallial development is ofVittaria-type andDrynaria-type, respectively. Frequency of sporophyte production was 44% in composite gametophyte populations, while no sporophytes were produced in isolate population. SinceM. alternifoliumwas found to have no capacity to form sporophyte through intra-gametophytic selfing, it is not a pioneer colonizer in barren land. Instead, it reproduces by inter-gametophytic selfing and also possibly by crossing. The main cause of rarity could be genetic barriers and over exploitation for economic purposes. Conservation of this taxon in the natural habitat is urgently required.
