xxxu 



BOTANY. 



= r. n.™nr.li. LemnaValdiviana. SchoUeragraminea. 



SoMagonemoralis polyrrU^a. Scirpus Torreyi. 



Utriculariammor. Arc Sparganium eurycarpum. Subarc. Care, aristata. Arc. 



GenHanadetons.. Mt. Arc. p^„t,Lgeton lonchites. Agrostis elata. ? 



RumexBntannica. gramineus. Arc. Muhlenbergia sylvatica. ? 



CeratophyUumdemcrsum. perfoUatus. Arc. Eragrostis Purshu. 



Parietaria Pennsylvamca. Mt. f 



The remaining plants of the valley flora are those which in a much 

 greater variety both of genera and species occupy the drier sandy or graveUy 

 portions of the valleys and the foothills, and are consequently subject to a 

 greater extreme of heat and drought. Many of them are low or dwarfed 

 annuals, often varying much in size and habit with the circumstances of their 

 growth,' usually starting with the rains of autumn, flowering in early spring, 

 and hastening to a quick maturity. With the first heats of summer they are 

 burned away and speedily vanish. Others are stouter and hardier, frequently 

 becoming more or less woody, or are biennials or perennials springing from 

 bulbs or from thick and usually deepseated roots or root-stocks, and in the 

 partial protection afforded by the larger shrubbery are able to maintain their 

 growth till later in the season. By the middle of July, however, the far 

 greater number have wholly disappeared and only the more woody based 

 perennials are left, except in favored localities. 



These comprise all the peculiarly "desert" species of this portion of the 

 Basin. Of the entire number (305) one-third (94) are so far as known 

 strictly confined to the Basin, and on the whole southern, quite a large num- 

 ber extending southward into the Mohave and Colorado deserts and half a 

 dozen southeastward to New Mexico or even Western Texas. Another third 

 (84,) the first section of division (&), range only westward, some to Southern 

 California but nearly one-half (38) to Oregon or Washington Territory, 

 though only a single one, Matricaria discoidea, is reported from farther north. 

 Of the 106 which are found in the Rocky Mountain region, 63 belong also 

 to the Pacific slope and as many more pass east of the range, though only six 

 are arctic or subarctic. There are also here at least 20 Mexican species and 

 53 others that have been collected in Arizona. Of the 21 still more eastern 

 species in division (c.) five are not found upon the Pacific side and six reach 

 the arctic or subarctic portions of the continent. About half extend into 

 Mexico or Arizona. As many jis in the last group (51) are noted as ascend- 

 ing above the foothills, but rarely to any great altitude. Only Artemisia 

 tridentata, Gilia congesta, and one or two other species sometimes reach the 

 summits of the higher ridges. 



