24 BULLETIN 460, U. S. DEPARTMENT OF AGRICULTURE. 
species. So keen an observer as Dr. Engelmann could hardly have 
mistaken the foliage of any other Rocky Mountain pine for that of 
Pinus aristata. The first authentic specimens of the tree were, how- 
ever, collected by Dr. C. C. Parry on Pikes Peak, Colorado, in 1861. 
Bristle-cone pine received its present technical name, Pinus aristata, 
in 1862, since which date the history of the tree has been practically 
free from confusion. In 1878 it was designated as P. balfouriana 
var. aristata Engelm., but this suggested relationship to the Califor- 
Nia species is not generally accepted.” 
DISTINGUISHING CHARACTERISTICS. 
Bristle-cone pine varies in height and form from a half-prostrate 
twisted shrub, at very high elevations, to a bushy-crowned tree from 
35 to 40 feet, in the situations more favorable for growth. Ordinarily 
it is from 15 to 30 feet high and from 12 to 18 inches in diameter, 
the tallest trees being from 20 to 30 inches or more in diameter. The 
trunk is clear of branches fcr about 6 or 8 feet. The rather wide 
bushy crown of long, drooping lower branches and of irregularly long 
upright top limbs is characteristic of single trees or those in open 
stands on wind-swept slopes. In denser stands, in less exposed situa- 
tions, the crown form is narrower. Young trees have a distinctly 
pyramidal crown with short rather thick branches which stand out 
from the stem at right angles. The bark of old trunks is a dull red- 
dish brown and rather shallowly furrowed, the main flat ridges being - 
irregularly connected by narrower diagonal ones. Bark on the trunks 
of small trees and of the large limbs of old trees is smooth and chalky 
white. 
The deep green foliage is densely clustered at the ends of the 
branches, the needles being closely pressed down (Pl. XV), in this 
respect closely resembling the true fox-tail pine (Pinus balfouriana). 
As a rule, the leaves are borne in clusters of 5, occasionally of 4, 
and are about 14 to 14 inches long (Pl. XV, c). The leaves of each 
season’s growth persist for approximately 12 or 14 years. 
1 Pinus aristata was first introduced into cultivation at the Harvard Botanic Garden, 
by Dr. Asa Gray, to whom Dr. Parry sent seeds from Colorado in 1862. Dr. Gray raised 
a number of seedlings from this seed, and Prof. C. S. Sargent (Gard. and Forest, X, 470, 
1897) states that some of these plants still growing in the vicinity of Boston had in 35 
years attained heights only of from 12 to 18 inches, from which it would seem that the 
species is not adapted to that part of our Atlantic region, and certainly not to regions 
farther south. A trial of this pine near Portland, Me., shows decidedly better results. 
Mr. H. A. Jackson writes that trees he raised from seed planted in 1908 are now (1917) 
24 feet high and growing thriftily. Accounts differ as to when this pine was first intro- 
duced into England, the date given in one instance (Gard. Chron. IV, 549, 1875) being 
1863, and in another (Gordon, Pinetum, ed. 2, 292, 1875), 1870. It appears to be better 
adapted to the climate of England, where, according to Elwes and Henry (The Trees of 
Great Britain and Ireland, V, 1055, 1910) trees have attained heights ranging from 15 
to 25 feet during a period, probably, of 35 to 40 years. 
