A Monographic Study of the Genus Palafoxia and Its Immediate Allies

Abstract

It has been the purpose of this study to evaluate taxonomically on the basis of morphological examination the generic and specific entities involved in Palafoxia and its immediate allies, southern United States and Mexican representatives of the tribe Helenieae in the Compositae. Early in the history of the group considered, it was recognized that more than one generic element was present in this complex of related plants, but the exact nature and scope of these units were not known. There have been many different interpretations of the generic relationships and considerable shifting of the species from one genus to another without satisfactory results. From the present study it is concluded that there are three distinct genera in the group, namely, Othake, Polypteris, and Palafoxia, and that in the last genus two elements are enough different to substantiate division into two subgenera. The second part of this problem has been to determine the generic relationships of the species involved and to examine their validity. In Othake delimitation of the species has been unsatisfactory because of the great variability of the plants; certain species have been based on specimens which, more thorough collecting proves to be extreme forms scarcely equal in rank to the recognized entities. It has therefore seemed advisable to reduce two species to varietal rank and to place another in synonymy. A somewhat similar situation in Palafoxia warrants the reduction of a species to a variety. Morphological examination was based on herbarium material in the Missouri Botanical Garden and on living material observed and collected in Texas by the writer. Type specimens and additional material were obtained from the Gray Herbarium, the Academy of Natural Sciences of Philadelphia, the New York Botanical Garden Herbarium, and the S. M. Tracy Herbarium of A. and M. College, College Station, Texas. It is with sincere appreciation that the kindness and assistance of Dr. Jesse M. Greenman is acknowledged. To Dr. George T. Moore, for the facilities of the library and the herbarium, and to Mr. H. B. Parks, for many specimens from Texas, thanks are also expressed.