Monographs Details: Rhamnus
Johnston, Marshall C. & Johnston, Laverne A. 1978. Rhamnus. Fl. Neotrop. Monogr. 20: 1-96. (Published by NYBG Press
Discussion:Rhamnus Linnaeus,one of the three genera of Rhamnaceae in which each of the fleshy fruits contains two or more free stones (Johnston, 1974), comprises more than 125 species. We usually think of Rhamnus in terms of north-temperate shrubs, but members of the genus are well represented in the Old World tropics and slightly less well in the Neotropics, where we find shrubs and small trees and even trees “five feet DBH and 150 to 200 feet tall” (D. E. Breedlove, in litt. 9 October 1976). Although the temperate-zone species, especially the European ones, are relatively well known and understood taxonomically, those of the tropics have been neglected.
The two most important systematic treatments of the American species of Rhamnus sensu latiore published in the last 40 years both suffer from a provincial outlook perhaps even more severely than do most monographic works. C. B. Wolf’s (1938) revision of the North American including Mexican and West Indian taxa is careful and thorough as to the species of the United States and Canada and especially as to the Californian taxa, with which the author was familiar in the field, but his treatment of the Mexican and West Indian taxa bespeaks more haste than understanding. He misused at least one name as a consequence of failure to examine the type, and confused under one name two common tropical Mexican species.
The publication 11 years later of a world-wide revision (V. I. Grubov, 1949), based almost solely on materials in the Leningrad herbarium, failed to improve the situation. Although his treatment of the species of Europe and western Asia has apparently stood the test of time, Grubov’s detailed infrageneric system, replete with 10 sections and 54 series, was less successful. And the revision of the tropical American species can best be described as only partially convincing. Some American taxa, including species proposed by Wolf, were left untreated in the absence of material for study. Others were treated only on the basis of published data without first-hand study of collections; and a number of poorly characterized species were proposed on the basis of solitary specimens. The Russian work has languished in well deserved obscurity while for decades the herbarium-stores accumulated in appalling disarray, with the South American plants in particular passing under assorted later homonyms. In view of this disorder, and the proposals in recent years of several new tropical American species, it appears that the time is over-ripe for the publication of a new treatment. This paper presents a system for the plants of tropical America.