Two new species ofIsoetes (Isoetaceae) from Jeju Island, South Korea

We name and describe two new species,Isoetes jejuensis and I.hallasanensis, from Jeju Island, South Korea. These taxa are compared with related species in East Asia, including I.coreana andI. sinensis. The rugulate megaspore ornamentation ofI. jejuensis differs from those otherIsoetes species. Furthermore,I. hallasanensis varies fromI. asiatica in its microspore ornamentation and chromosome number, although both species have an echinate megaspore ornamentation. These new species are tetraploid (2n = 44), whereasI. coreana is hexaploid (2n = 66).