INTRODUCTION. 



This work is an extension of the Flora of the Palouse Region published by 

 the authors in 1901. As enlarged, it covers all of Spokane, Whitman, Asotin, 

 Garfield. Columbia and part of Walla Walla Counties, Washington, and the 

 western portions of Kootenai, Latah, and Nez Perces Counties, Idaho. 



This region embraces the richest wheat lands of the Northwest, the high 

 rolling hills known locally as the Palouse country. The deep black wheat 

 soils are mainly residual, formed by the disintegration of the Columbia basalt 

 which covers the greater part of the region to the depth of 700 meters or more. 



The extreme southern part of the area includes the northern portion of the 

 Blue Mountains, here an upraised dome of basalt reaching an altitude of two 

 thousand meters. Separated only by the deep canyon of Snake River are 

 the Craig Mountains, Idaho, geologically a part of the Blue Mountain uplift. 



Near the Washington-Idaho line, but mainly in Idaho, a series of low 

 mountains extends from near Moscow northward. These mountains are all 

 formed of metamorphic rocks, mainly granite and quartzite. The highest 

 are Cedar Mountain, about 1,600 meters; Mica Peak, 1,595 meters; and Mount 

 Carlton, 1,720 meters. Outlying lower peaks of the same series are Kamiack 

 Butte and Steptoe Butte. 



The drainage of the region is in general westward. The principal rivers 

 are the Snake and the Spokane. The former has hewn an enormous canyon 

 through the basalt, which averages about 500 meters in depth but where it 

 cuts through the Blue Mountains is nearly twice as deep. All of its tributary 

 streams in the area considered, except the Clearwater, are small and flow in 

 shallow canyons. 



The Spokane river has filled much of its old valley with glacial gravels, 

 so that only its lower two-thirds now flows in a canyon. On the Spokane 

 gravels occur many species of plants not elsewhere found in the region. 



Lakes are numerous in Northwestern Whitman County, Spokane County 

 and adjacent Idaho. Little is known of their geological formation, but most 

 of them lie in the channels of existing or of geologic streams. 



The flora of the greater part of the region is Arid Transition, part of it 

 timbered with Yellow pine {Pinus ponderosa) , the rest treeless and character- 

 ized especially by the abundance of bunchgrass {Agropyron spicatum). The 

 bottom of Snake River canyon is occupied by an extension of Upper Sonoran 

 plants such as sagebrush and other species which commonly grow with it. 

 The highest dome of the Blue Mountains supports various Hudsonian plants 

 such as Subalpine fir, while a broad zone of Canadian Zone plants occupies 

 the slopes down to the Yellow pines. Conspicuous Canadian plants are 

 White fir, Engelmann spruce, and Mountain ash. 



The total flora of the region herein described consists of 20 Pteridophytes, 

 11 Gymnosperms, 270 Monocotyledons and 838 Dicotyledons. Some additions 

 to this list may be expected along the western borders of the area where a 

 number of Upper Sonoran plants are likely to occur, and most of the higher 

 mountain peaks require much more exploration. 



The material upon which this flora is based is mainly that contained in the 

 herbarium of the State College of Washington. Thanks are due to the 

 officials of that institution for encouragement and support in the preparation 

 of this volume. 



