INTRODUCTION 



11 



Upon the rocky ledges a small species of agave grows in abundance. The low leaves, which 

 are pointed with sharp spines, are very troublesome to the foot traveller; they are, however, 

 of some use to the IMexicans, who employ the strong fibres they contain in making coarse ropes. 

 The plant is known to the people of the country as *' Lechaguia." The table lands and valleys 

 are usually covered with an abundant growth of ** grama grass, ^' and among it are frequent 

 clumps of Dasyliriumj or ^^ bear's grass/' 



"We have here also several interesting species o^ Nydaginaceae^ belonging to the new genera, 

 AdeisantheSy Pentacropliis^ and Selenocavpus^ lately proposed by Dr. Gray. 



Among the annual plants of this district are several species oi Menizelia^ Perezia^ PeciiSy 

 Hymenatherumy &€,, also the pretty Eucnide lobata, which usually grows in almost inaccessible 

 situations upon the perpendicular faces of the limestone ledges. 



There are so many species that seem to be equally abundant that it i^ difficult to designate 

 any as being characteristic of the cretaceous district. 



VEGETATION OF THE niGHER BASIN TLAINS AND THE ADJOINING y^.. IAIN LI- 



The higher alluvial tracts, forming the basin plains before described, produce ^ n".*:_l 

 northern forms of plants, such as species of Q^aotJieraj Gauray Rlddtlliay Zinnia^ and Polygala. 

 We also find here the curious Peganum Mexicanum and Peteria scoparia^ the latter a pretty 

 plant of the family Leguminosce. The depressions in this alluvial region are covered with a 

 coarse grass, which presents an uniform dead brown color throughout the greater part of the 

 year. In the deep recesses and shaded valleys, the vegetation has a freshness unknown to that 

 of the plains- In these localities we encounter the upland live oak {Quercus Emory i, and tlic 

 nut pine, [Pinus eduliSj) and growing beneath these, Fitis incisa^ Clematis PitcJien\ Ungnadia 

 speciosa^ &g. The constant presence of water in the larger valleys is marked by the growth of 

 cotton wood and willows. 



VEGETATION OF THE EL PASO BASIN AND THE TPPER RIO GRANDE VALLEY. 



The vegetation of the immediate valley of the Rio Grande, and that of the country immediately 

 adjoining it upon either side, are strikingly different, and whoever passes from the valley, and 

 crosses the line of mountains which bounds it to the regions beyond, cannot but remark the 

 difference in the landscape, due to the presence of new plants. Upon the table lands which 

 spread out beyond the mountain barrier, the eye falls upon a great variety of plants, none of 

 which are seen in the more fertile valley. Among these are Fouquieria splendens^ Larrea 

 mexicanay Flourensia cernua^ Rhus microphylla, Condalia ohovata^ Koeherlinia spinosa^ and species 

 of Krameria^ Ephedra^ and Yucca. There the Cacti flourish in a congenial soil, and we find 

 representatives of the genera Opuntia^ Echinocactus ^ Blammillaria and Cereus. 



Among the numerous herbaceous and suffruticose plants of these localities we may mention 

 Ltvallia stnuata^ Greggia camporiim^ Eriogonum Ahertii^ and several species of Dalea ; plants 

 of the family Compositae^ are especially abundant^ and include among others Baileya midtira- 

 aiata, Bahia ahsinthifolia^ Porophyllum scoparium, Psathyrotes scaposa, Hymenatkemm acerosum^ 

 loicnsendta strigosaj Calycoseris Wriyldii^ Slepltanomeria minor End Pojiaesquia Neo-mexicana^ 



ine natural order of Nyctaginacece is represented hj Sdenocarpvs chenopodioides ^ BoerJiaavia 

 Wrightiiy and others. 



ihe prmcipal grasses of this region consist of the kinds known as ^^ bunch grass,'' and 

 belong to the genera Chondrosium and Bouteloua. The margin of the table land, where it 



