Comparative development of gametophytes ofOsmunda lancea andO. japonica (osmundaceae): Adaptation of rheophilous fern gametophyte

Development of the gametophytes of a rehophytic fernOsmunda lancea and a related dryland speciesO. japonica was examined, and adaptation ofO. lancea gametophytes to rheophytic habitat was discussed. The spores ofO. lancea were larger in size and contained larger oil droplets than those ofO. japonica. The germination rate was similar. In agar culture,O. lancea gametophytes grew more rapidly and reached reprudctive maturity earlier thanO. japonica, although there was no prominent gross-morphological difference in developing and mature gametophytes. Sporophyte formation ofO. lancea took place at roughly two times higher rate than that ofO. japonica. TheO. lancea gametophytes might be adapted to the periodically flooded habitat by shortening its life, which is a different strategy from that of the sporophytic generation.