Spore morphology and taxonomy of Isoetes in northeastern North America.

Taxonomy of Isoetes largely rests on megaspore and microspore wall ornamentation and spore size. These characters are reevaluated and the range of their variability is described (SEM photographs). Eight species of Isoetes are recognized for NE North America: I. macrospora, I. hieroglyphica, I. tuckermanii, I. riparia, I. acadiensis, I. echinospora, I. eatonii and I. engelmannii. Each species is provided with a revised list of synonyms, description, ecological notes and distribution maps. A key to species is provided. -from Authors