THE FOREST CANOPY oT 
however, is in furnishing each year a deposit of leaves 
and litter upon the forest floor. This disintegrates, 
enriches the soil, and thus hastens growth. It is in 
the canopy, and usually the upper part, where inflores- 
cence occurs, and a seed-crop is produced. This occurs 
usually at regular intervals, depending upon the spe- 
cies and the condition of the forest. These years 
are known as seed-years. 
An ideal forest consists of an evergreen conifer, 
such as the white pine, for an overwood, with a de- 
ciduous broad-leafed species, such as the beech, for an 
underwood. 
By the forest floor is meant not only the surface 
of the soil and surface covering, but also that part of 
the mineral soil which contains the rootage. Trees 
usually prefer a soft, well-drained, but moist mineral 
soil, on the surface of which there is a layer of de- 
composed litter, or leaf-mold. The formation of hu- 
mus, or leaf-mold, is called humificeation. It is a pro- 
cess of decay or disintegration in which soil fauna 
and fungi play a very important role. Nothing is 
of more importance to the forester than a knowledge 
of this process. Upon it soil fertility depends, and 
upon this depend the future forest and the amount 
of wood production. Besides furnishing food mate- 
rial, and especially nitrogen, which is essential to 
plant growth, the humus on the surface forms a 
