10 BULLETIN 460, IT. S. DEPAETMEXT OF AGEICULTTTBE. 



a Scotch botanist, published the first account of the tree in 1853 under 

 the name Pinus fexilis, confusing it with the limber pine, which 

 was discovered and named 20 years before. Likewise, in 1857, Dr. 

 Newberry erroneously referred to it as Pinus cembroides. It re- 

 mained for Dr. George Engelmann to describe this pine technically 

 and to establish its present name, Pinus alhicaulis, in 1863. The 

 French botanist Carriere named it Pinus shasta in 1867, while as 

 late as 1880 Dr. Engelmann, then concluding that it was a closely 

 related form of the limber pine, renamed it Pinus flexilis var. albicau- 

 lis. As now known, however, the white-bark pine is specifically dis- 

 tinct from our other white pines. 1 



DISTINGUISHING CHAEACTEEISTICS. 



White-bark pine has a low, long-branched, twisted, or crooked 

 trunk from 15 to 50 feet high and from 10 to 24 inches in diameter. 

 Taller and larger trees occur in protected situations. In the higher 

 wind-swept places it is often reduced to a sprawling shrub with enor- 

 mous branches spreading over .the ground. Young trees have distant, 

 regular whorls t)f branches which stand out at right angles to the 

 trunk, but in later life some of the upper whorls of branches develop 

 upward into long, willowy stems, giving the tree a loose, bushy 

 crown. The branches, especially near the trunk, are exceedingly 

 tough and flexible, so that the tree is able to withstand the fiercest 

 storms without being broken. 



The bark, even of old trees, is little broken, except near the base of 

 the trunk, where it is rarely more than one-half of an inch thick. Here 

 narrow cracks divide the bark into very thin whitish or brownish 

 scales, which when torn off reveal the characteristic red-brown inner 

 bark. Elsewhere the bark is rarely more than one-fourth of an inch 

 thick. Twigs of a year's and sometimes of two years' growth are 

 slightly downy. 



The dark j^ellow-green leaves (PI. VI), densely clustered at the 

 ends of the branches, are borne in bundles of 5, and are from about 

 1-J to 2f inches long. Shorter leaves occur on trees in the most ex- 

 posed situations (PI. YI, d) . The margins of the leaves are com- 

 monly smooth, but sometimes they have very widely separated minute 

 teeth. A cross section of the leaf shows two resin ducts (centrally 

 located on the dorsal or back side of leaf) ; occasionally a third resin 

 duct occurs on one of the lower sides. The leaves of each season's 



1 White-bark pine was probably first introduced into cultivation in Scotland through the 

 seeds John Jeffrey is said to have sent there from Mount Shasta. California, in 1S52 (fide 

 Elwes and Henry, op. cit., 1049). Elwes and Henry state that no plants appear to have 

 survived, and that the only specimens now known (1910) are seedlings growing in Kew 

 Gardens. It is probable that, like the limber pine of similar habitat, the white-bark pine 

 can not be successfully grown in eastern United States. However, it is in no way at- 

 tractive as an ornamental tree. 



