Yellow-flowered species of Linum in Central America and western North America

Abstract

Twenty-five yellow-flowered species ofLinum are found in western North America and Central America. These are divided into two unranked subgeneric groups, the “L. schiedeanum” and the “L. rigidum” com plexes. The former encompasses the species believed to be most primitive in North America. The greatest density and diversity of taxa of this segment of the genus are in east-central Mexico and point to that region as the probable area of establishment and differentiation of the yellow-flowered species in North America. TheL. rigidum complex includes the most highly specialized of the North American species and is believed to have been derived from some member of theL. schiedeanum group in comparatively recent times. The intermediate position ofL. sulcatum, a widespread North American species is discussed. Keys to, descriptions, and distribution maps of all the species are included.