CYTOTAXONOMY AND INFRASPECIFIC VARIATION OF AGROPYRON SMITHII RYDB.

Abstract

Agropyron smithii Rydb. is considered to be the correct name of the grass commonly known as western wheat grass. The pubescent variety molle has been found to have no distinct geographical distribution within the species and is therefore reduced to the rank of form. Many of the eastern localities recorded are attributed to introduction rather than to extension of the species range. Characters of pubescence and awning show relative uniformity within the clone but a much wider variation over the entire range. Spike, spikelet, and floret pattern is compared with those of related species. Somatic chromosome counts on 62 plants from points throughout the range indicate constant octoploidy (2n = 56). Chromosomal rearrangements appear to be slight. The species does not cross with several other species tested and is apparently self-sterile.