PINE TREES OF ROCKY MOUNTAIN REGION. Di 
straight and, in mature trees, free from branches for from one-third 
to one-half their height. The crown form of old trees is rounded, 
and that of young trees broadly conical. On old trunks the bark is 
about 2 inches thick, very dark or blackish brown, the close, separable © 
scales often showing light reddish brown in the deep, narrow furrows 
and also when freshly broken. 
Each season’s growth of the dark yellow-green foliage remains on 
the branches about two years, beginning to fall during the third sea- 
son. The sharp-pointed leaves (Pl. XVI), which are borne in 
clusters mainly of 5 (occasionally of 2-, 3-, and 4-, with the 5-leafed 
clusters), are from about 4 to sometimes 94 inches long, but com- 
monly from 5 to 7 inches long. The leaves produced each year vary 
greatly in length, even on the same tree, according to whether the 
season is favorable or unfavorable for growth. The leaves have close, 
persistent, basal sheaths from three-fourths of an inch to 1 inch long. 
The sheaths are a pale yellow-brown at first, later becoming grayish 
with exposure. The edges of the leaves have minute teeth (serra- 
tures). In cross section the leaves show three resin ducts, one in each 
corner of the section. 
The cones (Pls. XVI, XVII), which mature at the end of the 
second season, are one-sided (oblique) because of the greater devel- 
opment of the scales on one side. They are from 2 to 31 inches long 
and externally light yellowish brown, the ends of the cone scales 
being more or less glossy, but becoming ash-colored with age. The 
upper sides of the scales are a clear cinnamon-brown, while the lower 
sides are a deep purplish brown. On one side of the cones the ends 
of the cone scales have strongly developed, sharp-edged knobs, while 
on the opposite side the knobs are much less prominent. All of the 
cone scales terminate in a delicate incurved prickle, which is usually 
broken off in old, weathered cones (Pl. XVIT). As with the closely 
related western. yellow pine, the cones are borne on very short stems, 
which remain on the branches, with a few of the basal cone scales 
attached, when the cones fall from the trees. Most of the cones fall 
during late autumn or winter following maturity and after their 
seeds are shed. The seeds (Pl. XVII, a) are provided with broad 
wings which are a pale cinnamon-brown. Perfect seeds are borne 
under all of the cone scales, except the lower 3 or 4 layers, where 
they are abortive. The number of seed-leaves is unknown at present. 
The wood of Arizona pine is similar in general appearance to that 
of western yellow pine. It has a very thick layer of whitish or very 
light straw-colored sapwood, the heartwood being a pale reddish yel- 
low. In old trees the wood 1s especially narrow-ringed and rather soft 
and brittle. A cubic foot of dry wood weighs nearly 314 pounds, 
being slightly heavier than that of western yellow pine. The best — 
