34 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
sopis juli flora var. glandulosa ) and prickly pear ( Opuntia sp.) predom- 
inating. The latter is especially abundant throughout the thickets of 
mesquite and other small trees and bushes, all the way from Matamoros 
up the river to San Miguel, this lower portion being sub-arid. Before 
getting to San Miguel, some gravelly ridges are crossed showing the 
beginning of the transition to the more properly arid district. From 
here on to Las Chicharrones, the soil and vegetation much resemble 
those of arid western Texas. The town of General Trevino is situated 
in a dry and arid-like region. The change in the arid aspect of the coun- 
try is not marked until we arrive in the immediate vicinity of the town 
of Cerralvo, from which a fine view of the green mountain range to the 
west is had. On leaving Cerralvo, the road soon begins to encounter 
spurs from this range, which is known as the Sierra de Picachos, and the 
country becomes greener, betokening a greater rainfall. We cross a 
succession of these spurs and ridgefe, and soon encounter a region bris- 
tling with rather slim but tall and many-branched tree-yuccas, which 
reach to a height of 25 or 30 feet. In this region also the tree known 
to the Mexicans as anacahuita ( Cordia boissieri A. DC.) was numerous 
and in full bloom at this date, Sept. 29. Trees of some size grow in this 
region, giving a character to the woods that is not exhibited farther down 
toward the coast. The mountain ridges are now finally left behind, the 
town of Papagallos is reached, and not long afterward the road emerges 
from woodlands on to plains of mesquite and brush, the plains cut here 
and there by arroyos. On crossing these, the town of Doctor Gonzales 
is reached, just beyond which a river is forded; and still continuing over 
plains gradually getting more fertile we reach Marin, a town situated 
only 25 miles from Monterey. From Marin on to Monterey the country 
is green, with a usually good rainfall and a more varied vegetation. This 
is the identical route passed over by Dr. Wislizenus, in 1847, from Mon- 
terey to Reynosa. He gives a detailed account of his trip, with maps, 
including a profile of elevations. His observations give Cerralvo an ele- 
vation of about 1000 feet, and Marin about 1350 feet. (See Miscellaneous 
Document Ho. 26, First Session of 30th IT. S. Congress.) 
After reaching Monterey, the trip was made by rail to Venadito, 
Torreon, and El Paso, Texas. In southern Coahuila, between Venadito 
and Torreon, and nearer to the former, immense patches of a small Agave 
were traversed, very much like A. heteracantha of southern Hew Mexico, 
if not the same; and it was also noted that Dasylirion wheeleri grows ex- 
tensively in this region. This district must be in the neighborhood of 
5000 feet elevation. The change from the rather humid region of Mon- 
terey to the dry arid region of the tableland was made gradually between 
Monterey and Venadito, as the road worked up between the spurs of 
the table land. 
