36 PRACTICAL FORESTRY 
lationships of the various species with which he is 
dealing. On the control of the nature of the canopy 
depend the success and future condition of the forest. 
The canopy has several functions, the most im- 
portant of which is the fixation of carbon. The great 
bulk of the material which we call wood comes from 
the carbon-dioxid of the air. When wood is burnt, 
the part which burns comes from the atmosphere; the 
rest, represented by the ashes, comes from the soil. 
The conversion of the carbon-dioxid of the air into 
starch is the work of the leaves and green twigs of 
the canopy. This is only accomplished in the pres- 
ence of sufficient light, warmth, and moisture. The 
moisture comes from the soil, and is supplied by the 
rootage of the forest. The second function of the 
canopy is in shading, protecting, and manuring the 
forest floor. By shading the forest floor in sufficient 
degree, the growth of weeds, especially light-demand- 
ing weeds, is prevented. The drying action of sun 
and wind is also prevented. The forest floor is pro- 
tected also against the leaching and pelting force of 
heavy rain. Regeneration, or the growth of young 
trees on the forest floor, is prevented until it is de- 
sired, and then it is accomplished by letting in the 
light which stimulates seed production by the mother- 
trees, and permits germination on the forest floor. 
One of the most important functions of the canopy, 
