30 BULLETIN 460, U. S. DEPARTMENT OF AGRICULTURE. 
description of the tree’s characteristics) in his account of the dis- 
covery of the species published in 1836.1 
_ The botanical history of western yellow pine is full of perplexities. 
During the three-quarters of a century the tree has been known, no 
less than 15 different technical names have been applied to different 
or the same forms of the tree, some of which were described as distinct 
species and others as varieties. Much, if not all, of this confusion 
is probably the result of a study of herbarium specimens only, rather 
than of the tree as it grows under the different soil and climatic con- 
ditions within its extensive range (Map No. 10). 
DISTINGUISHING CHARACTERISTICS. 
Pinus ponderosa is a massive, straight-trunked tree with a long, 
narrow, open crown of hugely developed, bent branches. The nar- 
row columnar form of the crown, with its scattered branches, up- 
turned at their ends, is very characteristic. Often one or two large 
lower branches are separated from the crown by 20 or more feet of 
clear trunk. Trees grown from the first in an open stand usually 
bear branches close to the ground, retaining this long, low crown 
throughout life (Pl. XX). The trunk is cylindrical, with little taper 
until the large crown branches are reached. Its majestic size is sur- 
passed by no other native pine except the sugar pine of California. ° 
In general the height is from 125 to 140 feet, with a practically clear 
trunk of from 40 to 60 feet, and_a diameter of from 3 to 5 feet. 
Unusually large trees are from 150 to 180 feet high, while trees are 
said to have been found over 200 feet high. The largest diameter 
recorded is about 8 feet. The form of western yellow pine found in 
the central and southern Rockies ranges from 60 to 125 feet in height 
and from 20 to 30 inches in diameter, or occasionally somewhat 
larger. The bark of old trunks is marked by very broad, shield- 
like, russet-red plates, which may be from 3 to 4 inches thick, espe- 
cially near the base of the tree. The bark is peculiarly made up of 
small, concave scales. Younger trees, up to 2 feet in diameter, are 
quite unlike older ones in having dark red-brown or blackish, nar- 
rowly furrowed bark.?, Young shoots, which have a strong odor of 
orange when broken, are yellowish green and later brownish. 
i Companion to the Botanical Magazine, ii, 111. 1836. 
2TLumbermen in the range of western yellow pine distinguish two forms of the species,- 
one of which they call ‘ black jack ’’ and the other ‘‘ yellow pine.’”’ The two forms are 
botanically alike, but distinguished by striking differences in the color and markings of 
the bark, which appear to be due entirely to age. Trees up to about 150 years of age 
commonly have blackish, narrowly ridged bark and are, therefore, known as “ black 
jack,’ while trees older than these usually have hght reddish-brown bark broken into 
broad, flat ridges, such trees being called ‘“ yellow pine.’”’ The young growths of several 
eastern pines are also distinguished as ‘‘ black jack,’ most lumbermen who apply the name 
knowing, however, that it is an age designation rather than one of species. 
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