17

THE following paragraphs are quoted from the introduction to the "Vegetation in Chisos Mountains," ; based upon investigations made during the summers of 1931 and 1932. While applying specifically to the Chisos, it has general application also to the Davis, Guadalupe, Chenati, and other ranges, in proportion to their altitude and topography. Curiously, the Arizona cypress and Douglas spruce appear not to occur elsewhere in Texas besides the Chisos. Investigation of all the canyons leading down from the Davis Mountains' highest peak, Mt. Livermore, by L. C. Hinckley, has failed to reveal either of these species and neither is recorded, so far as I know from any other Texas location.

"The upper mountains are watered by springs and, in summer, normally, by almost daily afternoon rains. The plain is dry, for it receives little rain and has for the most part a high percentage of run-off, due in part to scant vegetation, in part to the nature of the soil, and in part to the torrential nature of precipitation. Only three of the upper waterways run normally. These are reduced to dry creek beds before they reach the foothills, and water runs in their lower reaches only after torrential rains. Grazing by sheep and goats is quite extensive in the foothills, but because of predatory animals is scant in the mountains.

"The vegetational physiognomy, like that of the remainder of the Trans-Pecos area, bears a close resemblance to the vegetation of Mexico. Desert shrubs such as sotol (Dasylirion), Agave, Yucca, ocotillo (Fouquiera), creosote bush (Larrea), and others, occur in great abundance upon the plains and foothills, extending, on drier slopes, even to altitudes of 6000 feet. Several Mexican species of needle grass (Stipa), triple-awn grass (Aristada) and other genera of grasses are important constituents of the various vegetational communities. Many other Mexican plants of lesser importance also occur.

Transactions of the Texas Academy of Science, Vol. XX., for 1935.1936; p. 6.