A biosystematic study of Digitaria sanguinalis Complex in North America (Poaceae: Paniceae)

Abstract

A biosystematic treatment was made of the Digitaria sanguinalis complex in North America. Materials for morphological, anatomical, embryological, and cytological studies were collected from throughout this geographic area. Based on these studies six species are recognized: D. bicornis, D. ciliaris, D. sanguinalis, D. nuda, D. setigera, and D. horizontalis. No new species of new combinations were described. New biological descriptions are given for each of the recognized taxa. Development of the pedicelled and sessile spikelet was examined on each of the taxa by means of scanning electron microscopy. These investigations showed that epidermal cell types, patterns of nervation, and pubescence were highly variable and that these characters cannot be consistently correlated with the recognized taxa of the complex. A correlation existed between epidermal macrohairs and bulliform cells on the lemma of the lower floret. True heteromorphism was found to be not typical of North American specimens of the complex. Detailed quantitative descriptions are given for leaf epidermal and internal anatomical characters. Based on the specimens examined, adaxial epidermal characters were used to differentiate among the taxa. However, the full range of variation within a single leaf, a specimen, or even between species is presently unknown. Anatomical characters of the leaf were found to be of the panicoid type. Based on a single sheath, radiating chlorenchyma, no endodermis, and centrifugal chloroplast it was concluded that all members of the complex were C(,4) subtype NADP-me. ...