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36. BULLETIN 460, U. S. DEPARTMENT OF AGRICULTURE. 
CHIHUAHUA PINE. 
Pinus chihuahuana Engelmann. 
COMMON NAME AND EARLY HISTORY. 
Chihuahua pine is a little-known species which has no distinctive 
common name in the United States, probably because it is not often 
distinguished by laymen from the other yellow pines with which it 
is more or less associated in our Southwest (map No. 12). It is 
known to a few lumbermen in Mexico as “black shortleaf pine.” 
The name “Chihuahua pine,” derived from the specific technical 
name, is suggested here as appropriate, because the tree occurs ex- 
tensively in Chihuahua, Mexico. 
Pinus chihuahuana was discovered in the western part of Chi- 
huahua by Dr. A. Wislizenus in 1846, and in 1851+ Dr. J. M. Bigelow, 
a botanist of the Mexican Boundary Survey Expedition, was the 
first to find it in our Southwest (vicinity of Copper Mines, southern 
New Mexico).2 Chihuahua pine was technically named and de- 
scribed as a species for the first time in 1848; from then until 1909 
there has been a general agreement among botanists regarding its 
claim to specific rank. In 1909 Dr. G. R. Shaw,’ believing it to be a 
variety of the Mexican Pinus leiophylla Schl. and Cham., designated 
it as P. leiophylla var. chihuahuana. He based the relationship upon 
the triennial fructification* of these two pines, and also upon the 
habit both have of sprouting from the stump.> Chihuahua pine is 
here maintained as a distinct species because of the commonly con- 
stant occurrence of its leaves in clusters of 3, the leaves of P. leio- 
phylla occurring almost invariably in clusters of 5. 
DISTINGUISHING CHARACTERISTICS. 
Chihuahua pine is a small or medium-sized tree as it occurs in our 
Southwest, varying from 35 to 60 feet in height and from 1 to 2 
feet in diameter. The fairly straight trunks are clear for one-half 
or two-thirds of their length, and the usually large branches have. 
an upward trend, forming a narrow pyramid-shaped crown. Com- 
pared with other associated yellow pines the foliage appears thin 
and pale.. The trunk bark, composed of thin, closely adhering scales, 
varies from a blackish brown to a very dark brown and is commonly 
bright red-brown in the deep rifts. It is from about seven-eighths 
1Fide Sargent, Silva, XI, 86, 1897. 
2Fide Torrey, Botany of U. S. and Mexican Boundary Survey, 209, 1858. 
’The Pines of Mexico, 14, 1909. 
*Dr. George Engelmann and Prof. C. S. Sargent discovered in 1880 that Pinus chihua- 
huana requires 3 years in which to mature its cones (Botanical Gaz., VII, 4, 1882). 
5 Chihuahua pine sprouts freely from stumps in its range within the United States; but 
the writer hesitates to rely upon this as a dependable indication of relationship to the 
Mexican Pinus leiophylla, for the reason that the sprouting propensities of Pinus echi- 
nata, P. rigida, and P. pungens, at some ages and under some conditions, could hardly 
be relied upon to show varietal relationship of these pines, 
