28 
now remain. These were set in the second-bottom land of the Missouri 
River, a much more favorable location than the one above cited in 
Kansas. The failure of pure-planted Cottonwood groves from ten to 
thirty years old has been so common throughout the West that special 
instances need not be cited. These are short-lived trees, and under the 
most favorable natural conditions, as in the immediate vicinity of 
streams, they thin out rapidly as they approach maturity; so that it is 
not surprising that they should die young when set in artificial groves. 
In the case of longer-lived species, such as Black Walnut, White 
_ Elm, the Ashes, and Oaks, pure planting is inadvisable because the 
trees grow so slowly in youth that it takes them a long time to shade 
the ground, thus either requiring continued cultivation through sev- 
eral years, an expensive practice, or else resulting in the checking of 
growth by grasses and weeds. Many species, under the most favorable 
conditions, do not make a shade sufficiently dense to prevent weed 
growth. Such trees are unfit for pure planting, not only on this ac- 
count, but because, having light foliage, the lower limbs continue to 
develop through a long period of years, and the trunk is thus either 
very Short, or else knotty, either condition impairing the value of the 
timber. 
The only places where pure planting is advisable is in swampy land, 
where the conditions are such that but few species will grow at all, or 
on very sterile lands, for the same reason. In all other cases a mixture 
of varieties is best, in which there shall be species especially adapted 
to various uses, set among nurse trees which will force them to grow 
tall and straight. 
MIXED PLANTINGS. 
Except for comparison, only mixed plantings have been tried in these 
experiments. The mixtures have been designed to include a varying 
number of species in different proportions, and have had always in 
view the light requirement of the several species used. Inexpensive 
quick-growing material has in all cases formed much the greater part, 
and the slower-growing species have been placed at greater distances, 
so that in thinning they would not be disturbed. This cheaper plant 
material is designed to nurse the more valuable sorts through their 
earlier years, and insure their becoming established. 
NURSE TREES. 
Trees which are planted with others in order to influence their growth 
are called nurses. Their purpose is to create conditions favorable to 
species that are difficult to establish, by affecting the light conditions 
surrounding them aud by furnishing soil cover. The value of a species 
as a nurse tree depends not at all upon its utility as timber, but 
altogether upon its habit of growth. In the treeless region a good 
