Megasporogenesis, megagametogenesis and embryogenesis of Liparis elliptica (Orchidaceae), with special note to the development of unique unitegmal ovule.

Megasporogenesis, megagametogenesis and embryogenesis of Liparis elliptica (family Orchidaceae, tribe Malaxideae, subtribe Malaxidinae) have been studied. It was shown that the L. elliptica embryo sac is monosporic and develops from the chalazal cell of the megaspore triad according to the modified Polygonum type. The embryo sacs are reduced to four-six nuclei. The suspensor is unicellular, spherical in shape, originating from the basal cell (cb). A unique feature of L. elliptica is the unitegmal ovule, which distinguishes this species from other members of the tribe Malaxideae. The seed coat is formed by an outer layer of the single internal integument. Reduction of the outer integument is a rare feature for epiphytic orchid species with photosynthetic leaves.