GAMETOPHYTIC DEVELOPMENT IN PTERIS-BERTER OANA (PTERIDACEAE, PTERIDEAE)

The development and characteristics of the sexual phase of Pteris bert eroana, endemic to the Archipielago Juan Fernandez, Chile, are reporte d. Spore germination is of the Vittaria-type, resulting in a uniseriat e gametophytic filament of three to five cells. Prothallial developmen t is of the Ceratopteris-type, by the development of a meristematic la teral zone, the young prothallus is asymmetric with unequal wings. The prothallia reaches sexual maturity in 120-150 days. The gametangia ar e of the common leptosporangiate-type. Sporophyte development was obse rved. The described morphogenetic characteristics of P. berteroana suc h as types of germination, prothallial development and gametangia, as well as the cordiform thallus, are evolutionarily derived (''advanced' ') characters shared by several groups of homosporic ferns.