Revision and cladistic analysis of Steinchisma (Poaceae : Panicoideae : Paniceae)

The genus Steinchisma Raf. (Poaceae: Panicoideae: Paniceae) is revised. Six species are treated in this work, in which exomorphological and anatomical characters are analyzed cladistically. Steinchisma comprises perennial spe cies that grow in open areas or near borders of rivers and streams. The pla nts possess membranous ligules, leaves lanceolate to filiform, inflorescenc es law and diffuse to contracted, with spikelets solitary on short or long pedicels; ellipsoid spikelets, glabrous, with the lower glume 1/3 to 1/2 th e length of the spikelet, upper glume and lower lemma subequal, lower palea as long as the upper anthecium, expanded at maturity, lower flower present , with three stamens, or absent; indurate upper anthecium; and a basic chro mosome number of x = 10. A similar anatomical pattern, intermediate between Kranz and non-Kranz species, was found in all species. A cladistic analysi s of Steinchisma was conducted in order to test its monophyly, and relation ships with the subgenera of Panicum. A key to the species is provided, as w ell as an anatomical description of the genus and photomicrographs of two s pecies; morphological descriptions, illustrations, and distribution maps ar e presented for all six species of Steinchisma. A new combination is made, Steinchisma stenophylla (Hack.) Zuloaga & Morrone.