468 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1885. 



course through the canon ; the last 15 miles are naked except near 

 a large spring, 2 miles from its mouth, where more Oottonwood are 

 found. 



The Bofecillos Mountains are drained by the Ternero on the west and 

 the Grapevine on the east. The former is a dry arroyo for about 5 

 miles above its mouth, then becomes a running creek for 5 or 6 miles, 

 with sparse Cottonwood, Texas Green Ash, Hackberry and Willow ; 

 this timber extends into several side canons. In gravelly ravines near 

 its head, the handsome shrub Cassia WisUzeni is common. 



The Grapevine, one of the prettiest tributary caiions of the Eio 

 Grande, contains a small stream which sinks and reappears in many 

 places, and many clumps of Cottonwood, Green Ash and Willow. The 

 Vitis wstivaUs f grows thriftily over the trees, while the Maidenhair Fern 

 (Adiantum Capilhis- Veneris) and Poison Ivy line the damp rocks. Here 

 were collected two rare and showy grasses, Gottea pappoph oroides and 

 Imperata arundinacea. 



Between the upper part of the Ternero and the Grapevine, including 

 the northern portion of the Bofecillos Mountains, lies a vast grassy 

 plateau which would be of great value as a grazing range were water 

 more plentiful. 



THE RIO GRANDE. 



FROM EL PASO TO ITS MOUTH. 



The valley, as it issues from the pass near which stands the town of 

 El Paso, widens out into a broad i^lain covered with a forest of Cotton- 

 wood whose dense foliage contrasts strongly with the tawny gray of the 

 bare slopes, the dark blue of the sharply outlined mountains and the 

 pale azure of the sky. 



The timber is confined to the river bottom and consists of Cotton- 

 wood* {Popuhis Fremonti, var. W isliise ni '^.), WiWo-ws and Sparse Ash 

 {Fraxinus pistacicefoUa., forma tomentosa of Torrey). The Willows are 

 two or three forms of Salix nigra, and Salix amygdaloides the larger and 

 prevalent si^ecies. 



The valley, below El Paso, varies in width from one to several miles 

 and, wherever irrigated, produces fine crops of corn, Mexican wheat, 

 onions, sweet potatoes, melons, cabbages, beans, alfalfa {Medicago sativa) 

 and red pepper. It also produces excellent fruits, such as grapes, pear, 

 and apricot. The Irish potato has not yet been successfully cultivated 

 on the Rio Grande. 



The Mezquit, as a low spreading shrub, remains prominent on high 

 ground. Its congener, the Screw-Bean {Prosopis pubescens), or Tornillo 

 of the Mexicans, growing in clusters 10 to 20 feet high, the separate 

 stems 8 to 10 inches thick, now becomes very abundant on the bottom. 



* Owing to the variable forms they affect, there is still some uncertainty iu the 

 differentiation of the Poplars of the Southwest. 



