Abortive embryonic structures within megaspores of Isoetes L. (Lycopsida - Pteridophyta)

摘要

Isoetes L. is a herbaceous, aquatic to terrestrial lycopod in which mega and microsporangia are produced on separate sporophylls (leaves). Megaspores are large and trilete whereas microspores are small and monolete (in majority). Thin serial sections through the megasporangial portion show presence of abnormal embryonic structures in the spore contents of the functional megaspores. Sterile spores do not have spore contents and are empty. This type of abnormal embryos have been reported for the first time in the genus Isoetes L.