PINE TREES OF ROCKY MOUNTAIN REGION. DAD 
than in the case of other conifers in its general range. Single-leaf 
pine occurs commonly in coarse, gravelly soils, shallow deposits over- 
lying granite, limestone, or shale and often in the crevices of rocks. 
It frequently forms pure, open stands over large areas, but usually 
it is associated with other trees, such as mountain mahogany, Utah 
juniper, mountain red cedar, oaks, tree yuccas, and occasionally with 
pifon. The largest trees and the pure stands occur mainly at the 
lower and middle levels of the tree’s vertical range. 
Pinus monophylla is very intolerant of shade throughout life. 
Seedlings grow faster, however, for several years under partial or 
light shade and also when protected from hot winds. 
This species bears some seed nearly every year and abundantly at 
intervals of two or three years. As in the case of other nut pines, the 
wingless seeds fall near the tree, whence they are sometimes dissemi- 
nated by flood waters. Birds and squirrels eat large quantities of 
them and Indians and whites collect them extensively for food. 
Exposed loose soil is the best seed bed, though even here germination 
occurs sparingly, so that reproduction is very scattered. 
LONGEVITY. 
Pinus monophylla is an exceedingly slow growing tree, reaching 
an age of from 100 to 225 years. Trees in thin, dry soil are espe- 
cially slow in their growth, specimens from 4 to 6 inches in diameter 
being from 80 to 100 years old. Trees occurring in deeper soils grow 
more rapidly, those from 10 to 12 inches in diameter being from 150 
to 160 years old. Further records are required to establish its extreme 
age limit. 
BRISTLE-CONE PINE. 
Pinus aristata Engelmann. 
COMMON NAME AND EARLY HISTORY. 
Bristle-cone pine is known to people in and near its high mountain 
habitat chiefly as “ fox-tail pine,” because of the close resemblance of 
its foliage to that of the true fox-tail pine (Pinus balfouriana), a 
California species. It is sometimes known also as “hickory pine.” 
An appropriate and distinctive name is bristle-cone pine, which is 
derived from the tree’s specific name, avistata (bearded), referring to 
the bristlelike prickles of the cone scales. 
It is probable that the earliest discovery of this pine was made 
in 1853 by Capt. J. W. Gunnison, of the U. S. Army, who collected 
a coneless branch in Cochetopa Pass (nearly southwest of Pikes 
Peak), Colorado, which Dr. Engelmann! believed to be of this 
1Trans. St. Louis Acad. Sci., II, 205. 1863. 
