Developmental studies on the gametophyte and apogamous sporophyte of the threatened fern <italic>Pteris reptans</italic> (Pteridaceae) in India.

Abstract<italic>Pteris reptans</italic> (Pteridaceae), a native fern of Sri Lanka, has its distribution in India with exclusive limited occurrence in the state of Kerala. The plants from Kerala were examined for their quantity of spores per sporangium, micromorphology using SEM, gametophyte and sporophytic developmental phases. Upon examination, it was discovered that the sporangium of all accessions contained 32 tetrahedral spores with a continuous cingulum and noticeable tubercles on both surfaces. Normal shaped spore frequencies per sporangia ranged erratically from 81% to 95%. The fern exhibited <italic>Vittaria</italic>-type of spore germination. Gametophytic development followed the <italic>Adiantum</italic>-type in early stages with further <italic>Ceratopteris-</italic>type growth. A thorough analysis of antheridial development was done, but throughout the whole investigation, no archegonium was seen. Without any gametic fusion, juvenile sporophytes were produced apogamously on the prothalli. The filamentous stage was retained until the third week after germination and the sporophytes started emerging from the 12th week. After 90–95 days no further sporophytes emerged. Developmental morphology of the sporophyte was studied by observing trends in frond characteristics. The study is the first report on detailed apogamous development of <italic>P. reptans</italic> and also describes propagation methods for <italic>ex-situ</italic> multiplication. [ABSTRACT FROM AUTHOR]