55 INTRODUCTION U ^ 0.03 AE E 
Upon the rocky ledges a small species of agave grows in abundance. The low leaves, which His 1 
are pointed with sharp spines, are very troublesome to the foot traveller; they are, however, 113 
of some use to the Mexicans, 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 баға of ““ оташа grass," and among it are frequent - Сон | 
clumps of Dasylirium, or ‘‘ bear's grass.’ 
We have here also several interesting species of Nyctaginaceae, belonging to the new genera,  :. ·. 
Acleisanthes, Pentacrophis, and Selenocarpus, lately proposed by Dr. Gray. " 
Among the annual plants of this district are several species of Mentzelia, Бей, Pettis, EEE 
Hymenatherum, &c., also the pretty Енетійе lobata, which usually grows in almost inaccessible i 1 
situations upon the "ИЕНЕН faces of the limestone ledges. Pa ied 
There are so many species that seem to be equally abundant that it is difficult to designate. 
Ї 3 any as being characteristic of the cretaceous district. 
VEGETATION OF THE HIGHER BASIN PLAINS AND THE ADJOINING MOUNTAIN RIDGES. zr ^ir : 
The higher alluvial tracts, forming the basin plains before described, produce a number of 
northern forms of plants, such as species of GZnothera, Gaura, Riddellia, Zinnia, and Polygala: | 
We also find here the curious Peganum Mexicanum and Peteria scoparia, the latter a pretty 
plant of the family Leguminose. 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 | 
суваг. 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 /тотуї, and the | 
nut pine, (Pinus edulis,): and growing beneath these, Vitis incisa, Clematis Pitcheri, Ungnadia 
speciosa, &c. The constant presence of water in the larger valleys is marked by the growth of ^ 
cotton wood and willows. 33 
.. VEGETATION OF THE EL PASO BASIN AND THE UPPER RIO GRANDE VALLEY. 
The vegetation of the immediate valley of the Rio Grande, and that of the country immediately. s: 
š ` 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 izi: 
i . which are seen in the more fertile valley. Among these аге Fouquieria iid. Larrea 3 i3 
` -< mexicana, Flourensia cernua, Rhus microphylla, Condalia obovata, Koeberlinia spinosa, and species. - ·:: 
of Krameria, Ж. апа Хиоса. | Hero the Cacti flourish in a congenial soil, and we find · 
^u Among the numerous herbaceous а хайнаг бан of these localities we may mention E 
Cama sinuata, Greggia camporum, Eriogonum Abertii, and several species of Dalea ; раза: : 2% 
22 diata, Bahia absinthifolia, Porophyllum scoparium E EE scaposa, H. ENE acerosum, 
Townsendia strigosa, Calycoseris Wrightii, Stephanomeria minor and Hofinesquia Мео-техїсапа. 
The natural order of Nyctaginaceae is represented by Selenocarpus — M Boerhaavia 
Wrightii, and others. КОЕ 
The principal grasses of this region consist of the kinds known as * bunch grass,' сам ЗР 
: отты to - Lm Chondrosium and Bouteloua, The margin of the table land, where it |... 
