CYTOTAXONOMIC NOTES ON SOME CIRSIUM SPECIES OF THE WESTERN UNITED STATES

Abstract

Chromosomes numbers of 17 species of the section Onotrophe of Petrak and of one species of the section Dermalolepis Petrak are given. The number 2n = 34, believed to be primitive, is found in 11 species; lower numbers, presumably reduced from 34, are found in two groups of species of the Onotrophe. The taxonomy and relationships of some species are discussed. A new species, Cirsium longistylum Moore & Frankton (2n = 34) from Montana, is described.