18 BULLETIN 24, U. S. DEPARTMENT OF AGRICULTURE. 
The sprouting capacity of stumps also depends upon their age. 
After 30 years of age it becomes weak and at 45 years almost ceases. 
Age, however. does not seem to aiiect the method of sprouting. Appa- 
rently the most vigorous sprouting capacity, as determined by the 
number of sprouts per stump, is somewhere between 15 and 25 years 
of age. It should be realized, however, that the smaller number of 
sprouts from stumps below this age is not an indication of lack of 
vigor, since a small stump can not for physical reasons support as 
many sprouts as a large one. 
The capacity to sprout, like reproduction from seed, is also gov- 
erned to a great extent by the ight supply. Vigorous sprouts do not 
develop under the shade of the forest. Im stands where only the 
best trees are cut, coppicing, because of the shade of ROUBLE 
trees, is almost sure to fail. 
Another factor of basic importance im aifecting coppice repro- 
duction is the season of cutting. Sprouts readily form after felling 
in winter or early spring, whereas stumps cut in summer or early 
fall seldom give rise to thrifty sprout growth. 
The conclusions just given apply particularly to the northern part 
of the Mississippi Valley in the vicinity of Red Wing, Minn. In 
the lower Mississippi Valley, where cottonwood is of larger commer- 
cial importance, very litile evidence of this form of reproduction 
was found. Comparatively few young, vigorous trees are cut. 
Lumbering usually removes only the larger mature trees, whose 
sprouting capacity is limited and whose stumps are partially shaded 
by trees left standmg on the ground. Lumbering, furthermore, is 
usually carried on most extensively in the summer and fall, when 
the sprouting capacity of the trees is lowest. Prebably this combi- 
nation of circumstances is responsible for the almost entire absence 
from the lower Mississippi bottom lands of cottonwoods of sprout 
origin. The adaptability of this system of coppice reproduction to 
the Mississippi region can be determined, therefore, only after actual 
experimentation. There is, however. little reason ito doubt that 
young stands of cottonwood in that region can be readily renewed 
by coppice, provided logging is carried on during the season of most 
vigorous sprouting and extended also to young trees. 
CHARACTER OF STANDS. 
Cottonwood occurs both in pure stands and in mixture with other 
species. Either of these conditions is unstable, the pure stand evolv- 
ing gradually into a mixed one from which the cottonwood may 
eventually be eliminated. This is due to cottonwood’s demand for 
full sunlight. As the old trees die they are succeeded by stands of 
more tolerant species which have come up under partial shade. In- 
fact, the very continuance of cottonwood in natural stands seems — 
