PINE TREES OF ROCKY MOUNTAIN REGION. 9 



Pinus flexilis usually occurs interspersed among other conifers, 

 singly or in small groves, the largest size being produced under these 

 conditions. Occasionally, however, it forms pure,, open growths of 

 stunted trees on exposed slopes and ridges. It is associated mainly 

 with lodgepole pine and mountain hemlock at higher elevations, 

 and sparingly with white fir and Douglas fir at lower altitudes. 



Limber pine grows best only in the full enjoyment of light, never 

 forming dense stands. It is similar in its requirements of sunlight 

 to the white-bark and bristle-cone pines, being less able to grow in 

 the shade, except when young, than other associated conifers. Lim- 

 ber pine is not an aggressive tree and rarely crowds out other species. 

 It is a moderate seeder, the amount of seed borne varying with the 

 region and elevation. Generally it bears the largest number of cones 

 in open stands at low altitudes, fruiting less abundantly in the denser 

 stands and at higher elevations. The cones are produced locally 

 about every year, while good seed years occur at intervals only of 

 several years. Many of the seeds are eaten by birds and squirrels 

 before they are shed. They are practically wingless and fall only 

 near the trees. Flood waters distribute the seeds irregularly and 

 the " hoards " of pine squirrels occasionally result in accidental 

 planting of uneaten seed. Germination of the seed, which at best 

 is only moderate, occurs most abundantly in moist mineral soil. 



LONGEVITY. 



Little is known now of the longevity of this pine. Trees from 13 

 to 22 inches through are from 200 to 300 years old. 



WHITE-BARK PINE. 



Pinus albicaulis Engelmann. 



COMMON NAME AND EARLY HISTORY. 



This species is commonly known to lay travelers in its high moun- 

 tain habitat only as " scrub pine," because of its stunted form in 

 exposed, wind-swept places. Those who know it botanically, how- 

 ever, usually call it white-bark pine, a name derived from the tree's 

 technical name, albicaulis (white stem), which has reference to the 

 characteristic chalky-white color of the bark. 



Pinus albicaulis was discovered in 1851 by the intrepid Scotch 

 botanical explorer, John Jeffrey. A letter he wrote, now preserved 

 at the Royal Gardens of Edinburgh, 1 states that he found the tree 

 " on the summit of a mountain near Fort Hope, Fraser's River," 

 central British Columbia, at an elevation of 7,000 feet. A. Murray, 



1 Fide Sargent, Silva, XI, 41, 1897. 



