8 BULLETIN 820, U. S. DEPARTMENT OF AGRICULTURE. 
eet in ae t, and only infrequently is 1t found over 8 er 9 aoe m 
ae eter and 50 feet in height. The small diameter of the trees is 
ex splstied by the fact that most. sf the stands are comparatively 
young. In the Upper Peninsula of Michigan jack pme stands occur 
x better soils and are favored with 3 a ayers rainfall than are thes 
ound in the lower peninsula. Therefore the average size of tie 
ie 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. Vill.) 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 compara tively fou 
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 ae 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 wees 8 inches in diameter and 50 feet in height. 
Tables 18 to 28 (appendix) indicate the form and growth of jack 
pime trees in regard to width of crown, thickness of bark, taper, and 
volume expressed in different units of measure. 
ROOT SYSTE*¢. 
oe deep, sandy soil where the water table is low, jack pme produces 
a lor Por scereiic taproot. On loose soil the Poe roots spread 
ee only a short distance and then descend parallel to the tap- 
root. Durimg the first year seedlings on this quality of scil 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 « the relatively large amount of 
food and moisture near the surface. At the same time a more or 
less pronounced taproot is sent oe though this does not develop 
as rapidly as on sandy soil. On fe and wet 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 pme growing in different regions 
and under different conditions. 
1See Forestry Quarterly, December, 1916. 
De 
