12 
The Colorado Experiment Station. 
common examples of this material. It is this compound in the 
spruces, aspens, and cottonwoods that makes them valuable for 
paper-making. When incorporated with the soil in the form of 
strawy manure or green crops, it decomposes slowly under the 
action of micro-organisms, keeps the land loose and open, and in¬ 
creases the water-holding capacity to a remarkable degree. Cellu¬ 
lose is a compound of carbon, hydrogen and oxygen, and is closely 
related to the sugars and starches in point of chemical composition. 
Certain bacteria of the soil, notably a group designated as Aniylo- 
bcicter, are known to feed upon it, and gradually to resolve it into 
carbon dioxide, hydrogen, methane and fatty acids. Here, again, 
the carbon dioxide is returned to the air. Some molds as well as 
bacteria can produce similar changes. However, the chemical re¬ 
action of the soil determines largely whether the decomposition will 
be brought about by bacteria or molds, since the former are active 
only in an alkaline environment, while the latter thrive best under 
acid conditions. 
Anyone who has ever strolled or ridden through our mountain 
forests must have been impressed with the immensity of the tim¬ 
ber waste. And yet is this waste? When we stop to think of the 
tremendous amount of energy and plant food which is being liber¬ 
ated through the decay and destruction of these fallen logs, the 
problem assumes quite a different light. The fertility of the moun¬ 
tain soils which wash into the gulches is too well known by every 
ranchman to need further comment. The fallen trees appear to re¬ 
main unchanged for years, but with the passing of time, they be¬ 
come spongy and punky through some agency not clear at first, 
and slowly but surely the hard, woody trunk is converted into a 
soft, brittle mass which eventually crumbles into a brown powder. 
This soon becomes incorporated with the soil and furnishes food 
for other plants. The decomposition which takes place here is, for 
the most part, a destruction of cellulose compounds, and is carried 
on not only by micro-organisms but also by some of the large, 
fleshy fungi, familiar to us as toadstools. In fact, fungi, or molds, 
are largely responsible for the destruction of the woody tissue. 
The larger forms initiate the attack on the surface, and send their 
thread-like “rootlets,” known as hyphae, beneath the bark and into 
the tissue. By means of enzymes and other chemical substances 
with which they are supplied, the wood is softened, and the way 
is paved for other fungi, and wood-eating insects. After the decay 
is well advanced, bacteria probably join hands with the other 
agents and hasten the final transformation. Thus, through the 
decay of timber, there are restored to the atmosphere carbon diox- 
