(Vol. 08, 2005-12) Taxonomy and Identification of Isoetes (Isoetaceae) in Texas Based on Megaspore Features

Scanning electron microscopy examination of Texas specimens of Isoetes revealed differences in megaspore ornamentation patterns of the proximal and distal surfaces that support the recognition of four species of the genus in Texas. These include I. butleri and I. melanopoda, both of widespread occurrence in the central United States, I. lithophila, a central Texas endemic, and I. piedmontana, which we report as new to the state. A key to species based upon megaspore characteristics, distributions, a limited list of exsiccate, and descriptions and micrographs of megaspores are included.