FISHES OF TEXAS AND THE RIO GRANDE BASIN. 
61 
higher ground the mesquit is abundant and the screw-bean (Prosopis pubes- 
cens) or tornillo of the Mexicans is very common. Further down the Rio Grande the 
cottonwoods become less abundant, but the mesquit and the other shrubby vegeta- 
tion increase, while still lower down the valley black willow ( Salix niger), the long- 
leafed willow ( Salix longifolia), water elm ( Ulnius crassifolia), green ash (Praxinus 
berlandieriana), which grows 2 to 3 feet in diameter and 40 to 50 feet high, and several 
other species of smaller trees and shrubs are abundant. On the lower Rio Grande 
and along the coast toward Corpus Christi are but few trees or bushes of any con- 
siderable size. The most important are the shrubby mesquit, huisache ( Acacia 
farnesiana), retama (Parlcinsonia aculeata), ebony, Texas persimmon, hackberry, and 
black willow. This is the region of the chaparral, great areas being covered with a 
scraggy, interlocking mass of shrubs all more or less thorny, or with stiff, spiny 
branches, the whole being almost impenetrable. According to Dr. Havard the princi- 
pal species represented are mesquit, granjeno, Texas persimmon, junco ( Kceberlinia 
spinosd), coyotillo, Acacia amentacea , Acacia flexicaulis, Condalia obOtrifoliata, Castela 
nicholsoni, Xantiioxylum pterota , Lippia lycioides, Berberis irifoliata, and Lantana 
camara. Among and over these grow such vines as Anredera scandens, Vitis incisa, 
Serjania brachycarpa, and Maximowiczia lindheimeri. 
Cactacece are of course abundant nearly everywhere on the uplands of Texas. 
Among the more common are several species of Mamillaria ( macromeris , meicantha , 
tuberculosa and heyderi), the strawberry cactus ( Gereus stramineus ), other species of 
Cereus ( chloranthus , paucispinus , and enneacantlius ), three species of jE Ichinocactus 
(longelumiatus, horizonthalonius, and intertextus), and several species of Opuntia (such as 
frutesceus r arbdrescens , andgrahami). Another conspicuous plant of southwestern Texas 
is the Mexican lechuguilla or agave ( Agave Jieteracantha ), which is found covering the 
limestone regions of that part of the State in impenetrable masses. The Texas mescal 
( Agave wislizeni ) and the Mexican maguey ( Agave americana ) are also common and 
conspicuous plants in this region. On the high mesa lands of southern and western 
Texas (but not on the Llano Estacado) the Spanish bayonet (Yucca baccata) is 
abundant; in places it grows to a height of 25 to 30 feet, is a foot or more in diame- 
ter, and is the most characteristic plant of the wide slopes leading up to the bases of 
the mountains. 
DRAINAGE. 
Texas is drained by the Arkansas, the Red, and the Rio Grande, together with 
a large number of smaller streams which reach the Gulf at various points along the 
400 miles of coast line which the State possesses. The Rio Grande and the Arkansas 
have their headwaters not far from each other in a limited district in Colorado and 
New Mexico, but they reach the sea through mouths a thousand miles apart. The 
most northern counties in the Panhandle of Texas are drained by. the North Fork of 
the Canadian River, while those lying next south are drained by the South Fork of 
the Canadian, both belonging to the Arkansas system. 
The portion of the State which belongs to the Arkansas basin has an area of about 
12,000 square miles. The South Fork of the Canadian rises in the Rocky Mountains, 
in the northeastern part of New Mexico not far from the headwaters of the Pecos, and 
flows entirely across the Panhandle in the northern part of the Llano, through which 
it has cut a deep canyon. This river is about 900 miles long, but is in most of its 
course a rather shallow stream. 
