Foliar Micromorphology of Cornus

Abstract

HARDIN, J. W. AND Z. E. MURRELL (Department of Botany, North Carolina State University, Raleigh, NC 27695-7612 and Department of Biology, Western Kentucky University, Bowling Green, KY 42101-3576). Foliar micromorphology of Cornus. J. Torrey Bot. Society 124:124-139. 1997. The 50+ species of dogwoods exhibit a Laurasian distribution pattern with centers of diversity in eastern Asia, North America, and Central America, plus a few scattered species in Africa, Europe, and South America. The genus is treated here sensu lato although some earlier treatments split it into nine genera. Foliar micromorphology, using SEM, shows a wide range of variation in several features. Epidermal cells vary from flat or slightly convex to papillose. Cuticle is smooth to striated or coronulate. Epicuticular wax may be present or absent. The basic and most common trichome is the flat, symmetrical, unicellular, dolabrate type often with calcium carbonate crystals on the surface. Six trichome modifications are formed by the asymmetry and orientation of the two arms and the elongation of the arms and basal stalk. These trichome modifications are considered to be derived (apomorphic) and form various vestiture types (strigillose, strigose, pilose on the veins, or pilose throughout) possibly reflecting adaptations to different environmental pressures and/or insect predation. The characters were coded for presence/absence and subjected to phylogenetic analyses at both the subgeneric and species levels to determine if the micromorphological characters correlated with current hypotheses of relationships within Cornus. Although the results suggested that there was little phylogenetic information at the subgeneric level, analyses generated unique hypotheses of species relationships within subg. Cornus, Cynoxvlon, and Svncarpea.