Role of morphological characteristics of leaves and the sporangial region in the taxonomy of Isoetes in northeastern North America

Vegetative features have often been used as key characters in distinguishing between species of Isoetes as well as for supportive evidence in taxonomic treatments of the genus (Pfeiffer, 1922; Fernald, 1950). As part of a larger taxonomic study of a group of species within this genus from northeastern North America, morphological characteristics of the vegetative body were studied in order to assess their taxonomic significance. Taxonomically valuable character states were considered to be those that correlated with distinctive spore ornamentation (Kott & Britton, 1983), cytological (Kott & Britton, 1980), chemical (Kott & Britton, 1982a) and biological groupings (Kott & Britton, 1982b). Those characters that varied within taxa and overlapped greatly among taxa were considered of no taxonomic value. Characters of the leaf, corm, roots, velum, ligule, leaf margins, and sporangium were investigated.