THE ECOLOGICAL RELATIONS OF THE VEGETA- 
ION OF WESTERN TEXAS. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORA- 
TORY. XXX. 
WILEIAM L. BRAY. 
(WITH TWENTY-FOUR TEXT FIGURES) 
[Concluded from p. 217.| 
SEMI-XEROPHYTIC FOREST OF THE HIGH MOUNTAIN SUMMITS 
AND WATERED CANONS OF TRANS-PEcos Texas.—On the higher 
Guadalupe and Davis mountains the annual rainfall is several 
inches greater than the normal for that meridian, and greater 
than in similar altitudes in the mountains of the Great bend of 
the Rio Grande. The mean temperature also, because of the 
northerly position and altitude, is enough lower than in other 
portions of trans-Pecos Texas to make these mountain summits 
a distinct zone, namely the Transition zone. On these higher 
summits and in the well-watered cafions leading down from 
them, the extreme xerophytic conditions of the region are very 
much modified. This becomes very evident in the aspect of the 
prevailing formation, an almost mesophytic forest. 
The chief elements of the formation are as follows: Pinus 
ponderosa, on Guadalupe peak at gooo feet, attains a height of 
50 feet, with trunk 2 feet in diameter ; on the Davis mountains 
it has yielded clear lumber 18 inches wide. This is the prevalent 
species, occurring in places in pure formation, as at the “ pinery 
northeast of Limpio peak. Next in prevalence is Pseudotsuga 
taxifolia, which attains similar dimensions. Pinus flextlis reaches 
a diameter of scarcely more than a foot. Below there begin 
Pinus edulis, Funiperus pachyphloea, and the oaks of the xero- 
phytic slopes. The summit formation descends into the upper 
cafions a short distance. 
In addition to the species just cited, the following transition 
262 [ocTOBER 
