233 
subject of more research than they are. It may be thought that the 
clearness of the atmosphere in Colorado, bringing a superabundance of 
sunshine, is a great gain to all life. It is so to many conditions of 
human existence, but not to all, and under certain circumstances is d1- 
rectly injurious to vegetation. True it is that ‘ Light is the source 
of life,” but its very greatness and power require tempering, softening, 
and restraining, like tire and water. Sunlight and warmth start the 
machinery of a tree and produce the chemical combinations which are 
necessary to its life. Under its influences the mineral substances, drawn 
from the soil by its roots, are combined with the carbon and other mat- 
ters received from the air through the leaves, and the resultants, 
carbon and oxygen, are produced, the former for the building up of the 
various parts of the tree and the latter by exhalation into the atmos- 
phere, for the use of animal life. This machinery of the tree, under 
proper conditions, works as steadily and smoothly as the best regulated 
engine. But if the speed of an engine is increased too greatly there fol- 
lows vibration, increased friction, a falling out of adjustment, and soon 
it becomes worn, broken, and useless. So with a tree, the rapid action 
produced by the bright sun and clear air may draw too greatly upon 
ifs means of subsistence, more or less limited in this dry region, and 
the tree, unable to keep up the supply, dies. 
Thus we have found that trees in Colorado, especially in the section 
around Denver and Colorado Springs, sutfer principally from extreme 
temperatures with sudden changes, and from lack of rain to supply the 
needed moisture for the roots. When water is supplied artificially by 
irrigation, they still sufter from insufficient humidity in the atmosphere 
_to provide moisture for the leaves and stems, from rapid evaporation 
caused by the dryness and rarity of the atmosphere and the frequency 
_of winds, and from the clearness of the sky, or lack of cloud and mist to 
intercept the dry, scorching rays of the sun, and to prevent the sudden 
changes of heatand cold. Truly, indeed, this is not a favorable climate 
for the growth of trees. But we have dwelt more particularly upon the 
injurious qualities of the elimate. The conditions are not all unfavor- 
able, and notwithstanding the many drawbacks trees will and do grow 
in Colorado and fulfill the objects for which they were created. 









































ADVICE TO TREE-PLANTERS. 
We have already, from time to time, indicated some of the peculiar 
modes of treatment necessary for the successful growth of trees in this 
region, and a brief summary of these will be useful. 
_ Those localities should be selected for planting, if there be a choice, 
which, by the configuration of the ground will be most protected. 
Among the mountains, this will be on the northern slopes, where the 
rays of the sun are least powerful and evaporationis leastrapid. If pos- 
ible the useful operation of plowing and cultivating the ground before 
janting should be performed. In this way the soil, besides being 

