at ELEMENTARY FORESTRY. 
grower cannot rely upon such methods, because they are too 
expensive or entirely impracticable. He may indeed plow for 
his first planting and cultivate the young trees, but alter a few 
years cultivation will become impossible and the effects of the 
first preparation will be lost. He must therefore attain his 
object in another way, that is, by mulching the soil. The 
shading is done at first by planting very closely, so that the 
ground may be protected as soon as possible from sun and wind. 
The shade should be maintained well throughout the life of the 
tree, even if more planting is necessary to accomplish it, and if 
in later life the trees get thin in the tops or die out, it may 
become necessary to plant underbrush to protect the land. 
Undergrowth in Forests may be rather injurious in pre- 
venting the proper development of young trees, but it is gen- 
erally very beneficial in retarding evaporation from the surface 
soil, in retaining the snow in the spring and in killing out grass 
and weeds. 
Forest Floor is a term used to indicate the mulch on the 
eround in forests. This is made up of the fallen twigs and 
leaves which remain on the ground, where they slowly decay 
and form a cover of rich mould or humus. This protective 
covering serves a most useful purpose; it permits the rain and 
snow waters to penetrate the soil without at the same time mak- 
ing it too compact, thus keeping the soil granular so that the 
air can enter, and in the best condition for conducting water, 
while at the same time it prevents washing away of the land and 
too rapid or excessive evaporation from the surface; the humus 
is also an active agent in aiding decomposition of the mineral 
substances in the soil. 
Subsoil. Tree growth is less dependent on the condition of 
the surface soil and more dependent on the subsoil than is the 
growth of agricultural crops. For instance, in the case of drift- 
ing sand overlying a moist subsoil, it has been found that where 
pains are taken to get the young trees started they will often 
do well although such land is poorly adapted to agricultural 
crops. There are many acres of land in Minnesota and Wis- 
consin that have such conditions, and they should seldom be 
entirely cleared of trees. 
Washing of Soils. The soils most likely to wash badly 
