Regional Variation Patterns in the Stemless White Violets

Abstract

In this and a paper to follow studies on the stemless2 white violets, initiated by the author in 1948, will be summarized. This research has resulted in several publications which are cited individually below. In the course of the research, many botanists have offered advice and encouragement to the author. Appreciation is especially due Dr. Gerald B. Ownbey of the University of Minnesota and Dr. William S. Cooper of Boulder, Colorado, for their assistance in early stages of the work. Dr. Cooper supplied much of tlhe information regarding the history of Orange Island, discussed under Viola lanceolata. The interest shown and advice given during the investigations by Dr. Ernst Mayr of Harvard University and Dr. Edgar Anderson of the Missouri Botanical Garden have been very helpful. Two studies used as guides in defining 'the aims of the present research were those of Woodson (1947) on Asclepias tuberosa and of Cain and Dansereau (1952) on the stemmed yellow violets of eastern North America. Certain of the methods used were borrowed from these studies. The object of the present paper is to provide a relatively exhaustive analysis of morphological variation from herbarium specimens and population samples and then to use these data in a consideration of the present evolutionary status of the group. This type of study is frequently found in recent literature, but, since Brainerd's investigations (summarized in his work on hybrid violets, 1924), little research of this nature has been done in Viola. Most of the studies in Viola, such as those of Valentine (1941, 1950) and Clausen (1924, 1926, 1930, 1931), have been concerned with cytological details and the relationships of chromosome number to morphological appearance and geographic range. The taxonomy of the stemless white violets is treated in a separate paper (Russell, 1955). The six species there recognized belong to the Group Stolonosae of the Subsection Plagiostigma, Section Nominium, of Viola. Four of the species, V. lnceolata, V. primulifolia, V. macloskeyi, and V. renifolia, h-ave the chromosome number of 2n = 24 and compose the Primulifoliae, and the remaining two, V. blanda and V. incognita, with the chromosome number 2n = 44 or 48 (Clausen, 1929), are placed in the subgroup Blandae (Gershoy, 1934; Bamford and Gershoy, 1930). All six of these violets are quite small, seldom exceeding a few inches in height. They have small, petiolate leaves arising from short, compact stems which