12 UNITED STATES AND MEXICAN BOUNDARY. 



"borders upon the valley is broken by deep ravines, and we find bere upon the sandy blufls a 

 growth of chaparral, made np principally of mezquit and the equally thorny acacias. In the 



Chilop 



Many of the 



already mentioned plants of the table land are found here, besides others, which are peculiar to 

 these localities, such as Bithyrce tvisUzenii, Ahronia melUfera^ Gilia longijlora, Lepidium 

 alyssoides^ Gaillardia pmnatijida, Polafoxia Ilooheriana and Tetraclea WrigJiiiiy a singular 



genus of Verb 



In the valley of the Kio Grande we 



frequently find a heavy growth of cotton wood and willows. 



Stromhocarp 



picbescens^ often occupies large tracts, accompanied by a dense undergrowth of i?acc7iam salicina. 

 The low saline places produce an abundance of Ohione canescens^ while on the higher ground; 

 Tessaria horealis is a common plant. 



A number of coarse composite plants are found in the valley, such as Texmenia encelioideSy 

 Coreopsis cardamine/olia and Aster spinosiiSy the latter often forming dense matted masses of 



considerable extent. 



The rocky crevices of the adjoining mountains furnish some of the most interesting plants of 



this region. "We here find Fendleria rnpicola^ Mortonia crassifolia^ Glossopetalon spinescens, 

 Agenia parvi/oUaj Bouvardia hirtella^ Tecoma starts^ Texmenia hrevi/oliay &c. 



The higher mountains of the Organ range have a vegetation possessing a somewhat alpine 

 characterj and bear a scattering growth of pines and oaks, beneath which flourish a number of 

 shrubby and herbaceous plants^, quite similar to those found upon the more lofty ranges farther 

 to the west. 



VEGETATION OF THE SIERRA MADRE. 



As we approach the base of the Sierra Mad re, passing over~ Ihe <^xt;eT»lj2:^basin-plain 

 already described^ a gradual increase in the elevation is marked by a disappearance of those 

 plants, which were common lower down^ and the presence of others wearing a more alpine 

 aspect. The surface is less bare than upon the plain below^ and is covered with a closely matted 

 grass, which gives a singularly rounded outline to the undulating land around the base of the 

 mountain. Along the lower rocky swells grows the beautiful CarphocJiete Bigelovii^ with 

 Anemone Ccirolinioiia^ Streptanthus linearif alius ^ Pentstemon Torreyi and Ftndleri are among 

 the characteristic plants of these localities. There are but few shrubby plants, several species 



Euh 



Frax 



and Juglans rupestris, (the large variety,) and in moist places an old Californian acquaintance^ 

 Aiiemiopsis Californiea makes its appearance. 



Upon the mountains oaks and pines are found, mostly Quercus Emoryi and Pinits edulis, 

 though in certain localities there is larger timber, consisting of Pinus ChihuaJiuana and Abies 

 Doiiglasii. The smaller woody growth here includes several species belonging to the Californian 

 mountain flora, such as Cercocarpus parvi/olius and Arctostaphylos tomentosus. 



Upon the summit of Ben More, further to the north, Dr. Bigelow discovered many plants 

 indicative of an alpine flora, among these were Frasera speciosa^ Euhiis Neo 

 Jtichardsonii^ and, perhaps, most remarkable of all, a small fern, Asplenium septentrion 

 European species not before detected on this continent. 



The abrupt descent through Guadaloupe pass, upon the wester 



ft profasiofl of evWgreen shrubs and flowering plants, including 



1 slope of the ridge, presents 



most of those which oocur on 



