SCANNING ELECTRON MICROSCOPY SURVEY OF LEAF EPIDERMIS OF SORGHASTRUM (POACEAE: ANDROPOGONEAE)

Scanning electron micrographs of the foliar epidermes of all 17 species of Sorghastrum are presented. A description of foliar epidermal micromorphology for the genus is followed by short descriptions of the individual species, emphasizing their epidermal differences. Papillar morphology is variable but taxonomically informative in distinguishing among the species of Sorghastrum. Based on the absence or presence of papillae, and differences in papillar morphology, three informal groups within Sorghastrum are recognized: 1) the nonpapillate group including S. balansae, S. rigidifolium, S. setosum, S. contractum, S. minarum, and S. viride; 2) the globose-papillate group including S. elliottii, S. incompletum, S. nudipes, S. nutans, S. scaberrimum, S. secundum, and S. trichopus; and 3) the elongate-papillate group including S. brunneum, S. stipoides, S. chasae, and S. pellitum. No correlation between papillar development and habitat is evident; however, a correlation exists between papillar development and the geographic distribution of the species of Sorghastrum.