36 BULLETIN 460, U. S. DEPARTMENT OF AGRICULTURE. 



CHIHUAHUA PINE. 



Finns 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 x 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. E. Shaw, 3 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 4 of these two pines, and also upon the 

 habit both have of sprouting from the stump. 5 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 



*Fide Sargent, Silva, XI, 86, 1897. 



2 Fide Torrey, Botany of U. S. and Mexican Boundary Survey, 209, 1858. 



3 The Pines of Mexico, 14, 1909. 



4 Dr. George Engelmann and Prof. C. S. Sargent discovered in 18S0 that Pinus chihua- 

 huana requires 3 years in which to mature its cones (Botanical Gaz., VII, 4, 1882). 



B Chihuahua pine sprouts freely from stumps in its range within the United States; hut 

 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. pnngens, at some ages and under some conditions, could hardly 

 be relied upon to show varietal relationship of these pines. 



