8 BULLETIlSr 820, U. S. DEPARTMEISTT OF AGRICULTUKB. 



feet in IieigKt, and only infrequently is it found over 8 or 9 inches in 

 diameter and 50 feet in height. The small diameter of the trees is 

 explained by the fact that most of the stands are comparatively 

 young. In the Upper Peninsula of Michigan j ack pine stands occur 

 on better soils and are favored with a heavier rainfall than are those 

 found in the lower peninsula. Therefore the average size of the 

 trees is larger and the quality is better. Trees have been found here 

 18 inches and over in diameter, 90 feet in height, and 150 years of 

 age. (See PL VIII.) Most of the stands are, however, composed of 

 young and small trees. 



On the eastern outskirts of its range in New England where a few 

 jack pine groves occur, the height of the trees is usually only from 

 15 to 20 feet. These groves are composed of comparatively young 

 trees. In Nova Scotia and eastern Canada also this species is of 

 small size. 



In the region north and west of Lake Superior and west of Lake 

 Winnipeg jack pine reaches its best development. Here it is occa- 

 sionally 90 feet in height and 20 inches in diameter. North of Lake 

 Winnipeg it seldom exceeds 8 inches in diameter and 50 feet in height.^ 



Tables 18 to 28 (appendix) indicate the form and growth of jack 

 pine trees in regard to v\ridth of, crown, thickness of bark, taper, and 

 volume expressed iii different units of measure. 



ROOT SYSTEM. 



On deep, sandy soil where the water table is low, jack pine produces 

 a long characteristic taproot. On loose soil the lateral roots spread 

 outward only a short distance and then descend parallel to the tap- 

 root. Dm'ing the first year seedlings on this quality of soil send a 

 taproot down from 6 to 12 inches, and develop very few laterals. 

 (See fig, 2,) On better soils a widely branched, surface-feeding root 

 system is developed early because of the relatively large amount of 

 food and moisture near the surface. At the same time a more or 

 less pronounced taproot is sent down, though this does not develop 

 as rapidly as on sandy soil. On shallow and v/et soils jack pine 

 develops only lateral roots. 



RATE OF GROWTH. 



Tables 1 to 8, inclusive, indicate the rate of increase in diameter 

 and height of single trees of jack pine growing in different regions 

 and under different conditions, 



1 See Forestry Quarterly, December, lOlC. 



