A systematic study of Salix section Cordatae in North America

Abstract

Twelve North American species of the section Cordatae of the genus Salix (willows) were studied to clarify their taxonomy. The sections Adenophyllae (Commutatae) and Wolfianae are included here in section Cordatae. Characteristics of the epidermal cells and pollen grains were of no taxonomic value. Chromosome counts were obtained for 6 of the 12 species. One other species had been counted earlier. There are three diploid species, two tetraploids, and a hexaploid. One other species (?) has both diploid and tetraploid populations. Flavonoid chemistry of the leaves was the most important and constant characteristic. Each species has a consistent combination of compounds different from those of all other species of the section. Cytology, chemistry, morphology, and distribution were well correlated. Keys to pistillate material, synonymy, descriptions, distribution maps, and representative specimens are included. Three new species are described and one varietal transfer is made.