PINE TREES OP KOCKY MOUNTAIN REGION. 43 



in accordance with the international rules of nomenclature adopted 

 at Vienna, Austria, in 1905, Pinus banksiana of Lambert (1803) is 

 the proper name for this pine. Fortunately, this is the technical 

 name under which jack pine was known to botanists from 1803 to 

 1892, Pinus divaricata having been revived in this country at the 

 latter date and maintained until about 1905. Three other technical 

 names, now reduced to synonymy, were also added during a botanical 

 history extending over a centry and a quarter. 1 



DISTINGUISHING CHARACTERISTICS. 



Jack pine varies in height from a stunted shrubby form only a few 

 feet high to straight well-formed trees from 25 to 60 feet in height 

 and from 8 to 20 inches in diameter ; occasional trees reach a height 

 of from 75 to 90 feet and a diameter of about 2 feet. Commonly, 

 however, it is from 25 to 30 feet high and about a foot in diameter. 

 The trunks are clear of branches for one-third or one-half the total 

 height ; in very dense stands longer clear trunks are common. Young 

 trees are rather densely clothed down to the ground with noticeably 

 slender branches, which, as a rule, trend sharply upward, forming a 

 pointed oval-shaped crown, which is relatively narrower in a dense 

 stand than in an open one. As the trees grow older, the crown be- 

 comes open because the longer, middle-crown and lower-crown 

 branches spread widely or curve downward, and sometimes upward 

 at their ends. The branches are strong and the twigs are notably 

 tough and flexible. Twigs of a season's growth are smooth and light 

 yellowish green, which changes to a deep reddish or purplish brown 

 by the second season ; the scaly terminal buds, three-sixteenths to one- 

 fourth of an inch long and about one-eighth of an inch in diameter, 

 are a dark cinnamon-brown. The thinnish dull red-brown bark of 

 mature trunks is narrowly ridged and furrowed, the main irregular 

 ridges being connected by smaller lateral ones. 



Compared with its frequent associates, the Norway pine and white 

 pine, this species has strikingly thin foliage, which is due to its short 

 distantly-set leaves. Fully matured leaves are a deep grayish green, 



1 There is no definite record of when Pinus banksiana was first introduced into culti- 

 vation in England, but it is believed to have been planted there some time prior to 1735. 

 The few trees now growing there, some of which were planted as early as 1839 to 1850, 

 had in 1909 attained heights of from 35 to 40 feet (fide Elwes and Henry, op. cit., 1112). 

 Many trees planted in England during these early years have gradually disappeared, 

 which, in the opinion of ElWes and Henry, indicates that the species is not well adapted 

 to the climate there. It has been extensively planted in Germany by the Government, 

 and to some extent also in Russia, where the trees made remarkably rapid growth during 

 youth. As might be expected, however, this species gives little or no promise for the 

 production of useful timber, its greatest usefulness being to form a tree cover on exceed- 

 ingly poor sandy and gravelly land where good timber trees will not grow. In the United 

 States, jack pine is one of the few conifers that has been successfully established in the 

 sand-hill region of western Nebraska, where the conditions for tree growth are exceed- 

 ingly unfavorable. 



