any aquatic tracheophyte plant of the genus Isoetes, with quill-like leaves at the bases of which are spore-producing structures: familyIsoetaceae, phylum Lycopodophyta (club mosses, etc)
quillwort in American English
(ˈkwɪlˌwɜrt)
noun
any of an order (Isoetales) of lycopods with short, fleshy stems and tufts of long, hollow, quill-like leaves whose bases contain spore cases