One of the most distinctive of the stemless blue violets of the upper midwest is Viola missouriensis Greene, the Missouri Violet. It is one of the approximately twenty-eight species of the Subsection Boreali-Americanae, Section Nominium, a group of violets somewhat notorious for their propensity for interspecific hybridization. Population studies were initiated in 1956 to define the members of this group more accurately and to determine the effect of hybridization upon their taxonomy and evolution. The Subsection Boreali-Americanae includes the so-called "stemless" (acaulescent), blue-flowered species. Within this group of species, two types of violets can be roughly distinguished: the entire-leaved species and the species with lobed or dissected leaves. As will be seen below, this distinction is not a good taxonomic one, though it is convenient for purposes of discussion.
Proceedings of the Iowa Academy of Science
©1958 Iowa Academy of Science, Inc.
Russell, Norman H.
"The Nature of Viola missouriensis Greene,"
Proceedings of the Iowa Academy of Science, 65(1), 96-101.
Available at: https://scholarworks.uni.edu/pias/vol65/iss1/10