GENERAL REPORT. 



Geographical Notes. The territory within which botanical collections 

 have been made in connection with the United States Geological Survey of 

 the 40th Parallel lies wholly within the limits of Northern Nevada and Utah. 

 It forms a narrow tract at no point exceeding seventy miles in width, between 

 the meridians of 11 1° and 120°, and extending from the parallel of 39° at the 

 southwestern limit to that of 42° at the northeastern. This region constitutes 

 the northern portion of what was at first designated as the " Great Basin," the 

 high plateau, without outlet for its waters, separated on the north by low 

 divides from the valley of the Snake River and continuing southward until it 

 merges into the desert of the Lower Colorado. Geologically considered, 

 however, as well as botanically, the term is now properly made to include the 

 whole similar arid stretch of country northward to the plains of the Colum- 

 bia in latitude 48°. 



The lofty and unbroken range of the Sierras bounds this section of the 

 Basin on the one side by its steep eastern slope, entering Nevada at only a single 

 point, where it throws over the border a high flanking spur, the Washoe 

 Mountains. On the opposite side lies the broad and nearly equally elevated 

 system of the Wahsatch, broken through by the Bear, Weber, and Provo 

 Rivers, which head among the peaks of the adjoining Uintahs. The interven- 

 ing space, 450 miles broad in latitude 42°, but narrowed by the convergence 

 of the opposing mountains to about 200 miles in latitude 37°, is for the most 

 part occupied by numerous short and somewhat isolated minor ranges, having 

 a general north and south trend, and at average distances of about twenty 

 miles. The bases of these ranges are usually very narrow, even in the most 

 elevated rarely exceeding eight or ten miles in breadth, the slopes abrupt and 

 the lines of foothills contracted, the mesas grading at a low and uniform angle 

 into the broad uninterrupted valleys. Over the larger portion of the territory, 

 and especially in Nevada, the combined areas of the valleys and the area 

 occupied by the mountains and accompanying foothills are very nearly equal. 



