The Live Oaks of the Series Virentes

Abstract

Key and descriptions of the 6 species and 1 variety are illustrated, distinctions being based upon morphological, geographic, and ecological (soil tolerance) data. New dispositions include Quercus minima Small X Q. chapmani Sarg. (r Q. rolfsii Small), Q. hemispherica var. maritima (= Q. phellos /3 maritima Michx. not Q. virginiana var. maritima Sarg., a misidentification), Q. virginiana Mill. (= Q. oleoides var. quaterna C. H. Mull.), and Q. oleoides var. sagraeana (= Q. sagraeana Nutt.). The series Virentes of Quercus comprises an aberrant natural group within the subgenus Lepidobalanus. Typified by Quercus virginiana, this small group has come to be known as the southem live oaks by reason of its concentration in the southeastern United States and by contrast with the many evergreen species of unrelated series in the southwestern United States, on the coast of California, and in Mexico. The species of Virentes occurring in the United States have, since their original proposals, been given two significantly different treatments. The less conservative treatment of Small (1913, 1933) credits six species to this area, while Sargent (1918) reduces such of these as he treated to the status of varieties under Quercus virginiana, simultaneously proposing additional varieties based upon less profound differences. Since neither of these authors concerned himself with the Latin American members of the series, the group has not yet been critically reviewed as a whole. The treatment accorded it by Trelease (1924) incorporated a compromise of Sargent's and Small's views with relatively minor additional modification. In evaluating Trelease's monograph, it must be remembered that he originally set out to do the Latin American species only and that he extended his treatment to the entire North American continent largely by incorporating the treatments of Sargent in the eastern United States and Rydberg in the western United States, subjecting neither to very critical analysis. The present treatment1 is motivated by the necessity of a review of the series in preparation for the statement of some evolutionary conclusions to which field and herbarium studies have led me. Although I readily admit the provisional character of some of the conclusions here presented, there are included some geographic, ecological, and morphological evidences of genetic relations (and genetic distinctions) not 1 I am indebted to the Associates in Tropical Biogeography and the Faculty Committee on Research, both of the University of California, for financial aid in prosecuting the field studies and to the National Science Foundation (project G-2713) for support of both field and herbarium studies upon which this work