Xxiv BOTANY. 



embraced within the limits of the survey, and for securing a somewhat com- 

 plete collection of the plants peculiar to the different sections as well as 

 seasons. 



As the area of the territory explored is occupied in nearly equal pro- 

 portions by the mountain ranges and intervening valleys, so we find the vege- 

 tation divided into two corresponding well-marked sections, which it will be 

 best to consider separately. In order also to arrive at the Basin flora proper 

 it will be necessary to distinguish those species which are peculiar to the 

 extreme eastern and western bounding walls of the Basin, to the Washoe 

 Mountains in Western Nevada as belonging rather to the flora of the Sierras 

 and California, and to the Wahsatch and Uintas upon the east as a part of 

 the somewhat distinct Rocky Mountain flora. Omitting, moreover, those 

 plants which have as yet been found only in the southern portions of Nevada 

 and Utah and which belong chiefly to the more desert region of Arizona 

 and Southern California, the remaining species of the Catalogue may be con- 

 sidered as giving a fair though by no means complete representation of the 

 flora of this section of the Grreat Basin. 



No portion of this whole district, however desert in repute and in 

 fact, is destitute of some amount of vegetation even in the driest seasons, ex- 

 cepting only the alkali flats, which are usually of quite limited extent. Even 

 these have frequently a scattered growth of Sarcobatus or Halostachys sur- 

 mounting isolated hillocks of drifted sand, compacted by their roots and 

 buried branches. This vegetation covering alike the valley plains, the graded 

 incline of the mesas, the rounded foothills and the mountain slopes, possesses 

 a monotonous sameness of aspect and is characterized mainly by the absence 

 of trees, by, the want of a grassy greensward, the wide distribution of a few 

 low shrubs or half-shrubby plants to the apparent exclusion of nearly all other 

 growth, and by the universally prevalent gray or dull olive color of the 

 herbage. 



To the absence of trees there seems to be but a single exception, in the 

 valley of the Truckee, where Populus monilifera and trickocarpa grow in con- 

 siderable numbers in the river bottom. Upon the Humboldt and Carson 

 Rivers they are rarely found, and in the higher eastern valleys the willow- 

 leaved P. halsamifera of the mountains scarcely ever follows the streams be- 

 yond the limit of the foothills. So as respects the second of the charac- 

 teristics mentioned, the turfing " buffalo" or " grama" grasses, which make 



