CHECKLIST OF THE VASCULAR PLANTS OF THE INTERMOUNTAIN REGION 



INTRODUCTION 



Fieldwork and herbarium studies leading towards the publication of an illustrated flora of the Intermountain 

 region were begun in 1931. More than 110,000 herbarium specimens, on which this flora will be based, have ac - 

 cumulated and been filed in the Intermountain Herbarium. Manuscript for several families and most of the illus- 

 trations have been completed. It seemed desirable to precede the projected three -volume flora with a checklist 

 so that the final study could be relatively free of omitted species. We learned in 1961 that the Forest Service was 

 interested in publication of such a checklist for an area that approximates its Intermountain Region. A cooperative 

 agreement was soon made between the Intermountain Forest and Range Experiment Station and the Intermountain 

 Herbarium, and work on the project started in the fall of 1961. 



The present checklist is the first attempt to include all the species of vascular plants that grow spontaneously 

 in the Intermountain region. It is expected that persons who use this checklist will add species to it. Such additions 

 will contribute to a more nearly complete listing of the plants of this large floristic area . 



BOUNDARY 



The floristic boundaries of the Intermountain region have been determined by the Intermountain Herbarium 

 staff after more than 3 decades of study. They have been modified many times during these years; so the area as 

 now delineated is a natural floristic unit . 



The area includes all of Utah, that portion of Arizona north of the Grand Canyon, most of Nevada, parts of 

 California that lie within the Great Basin, the sagebrush areas of southeastern Oregon, southern Idaho to the high 

 mountainous area on the north, and the Red Desert area of southwestern Wyoming. 



PHYSIOGRAPHY 



The area thus circumscribed includes parts of three physiographic provinces. The northern portion of the 

 Intermountain region, which drains into the Snake River and ultimately reaches the Columbia River, lies in the 

 section known as the Snake River Plains of the Columbia River Plateau. The southwestern corner of Wyoming, the 

 eastern half of Utah, and the northern portion of Arizona are within the Colorado Plateau Province. The remaining 

 and largest portion of the region lies within the Basin and Range Province. 



Details concerning principal mountain ranges and other physiographic features may be found in Fenneman's 

 PHYSIOGRAPHY OF WESTERN UNITED STATES. 



HISTORY OF PRINCIPAL BOTANICAL EXPLORATION 



Numerous collectors have traversed the Intermountain region studying the flora. Many species were first col- 

 lected by a handful of early explorers. The Lewis and Clark expedition (1804-1806) was the first important group to 

 collect plants in this area. Pursh described their collections in 1808. This expedition, like the Fremont expedition 

 of 1845, lost most of its plants. Only those plants hastily gathered on Fremont's return trip finally reached botanists. 

 Edwin James of the Long Expedition, and later Wyeth, traversed the northern edge of the Intermountain region. James 

 named some of his plants, notably Pinus flexilis, but sent most of them to John Torrey. Wyeth returned his plants to 

 Thomas Nuttall in Philadelphia, who described them. Nuttall, a man who many claim walked more of the United States 

 than any other person, came west, but he too stayed on the northern edge of the Intermountain region. 



Creation of the Topographical Corps of the United States Army in 1838 opened a new era of systematic botanical 

 studies of Intermountain flora. 



As people started moving west in large numbers, more routes for trails, wagons, and railroads were needed. 

 Abert, Sitgreaves, Ives, Whipple, Powell, Parry, Ward, and others led expeditions into the West. Torrey played 

 an important role in naming the new species collected by these explorers; but his pupil Asa Gray and his associates 

 in England, George Bentham and Joseph Hooker, also aided in naming many western American plants. 



Sereno Watson was one of the most important of the early plant collectors. He named many of the northern 

 Utah and Nevada species. Watson, upon returning east after King's expedition in the late 1860's, became associated 

 with Asa Gray and subsequently became the foremost authority on western flora. 



iii 



