16 BULLETIN 544, U. S. DEPARTMENT OF AGRICULTURE. 
terns, particularly those of the shallow-rooted species, spruce is much 
less windfirm when growing in crowded or pure stands than when 
growing in the open or in mixture with hardwoods. Thus the rela- 
tive size and the form of the crown of spruce growing under different 
conditions of density and association is an index of its comparative 
windnrmness. 
REPRODUCTION. 
SOIL, MOISTURE, AND LIGHT. 
Spruce finds its most favorable conditions for germination and sub- 
sequent early growth on the moist forest floor under cover of the not 
too dense stand of the selection forest. Here a suitable seedbed of 
moss, dead wood, and needle litter is found, which, being protected 
from exposure to the drying influences of sun and wind, affords suffi- 
cient moisture for germination and early development. That spruce 
appears to be selective hi its seedbed requirements, and that observ- 
ers are in disagreement as to whether it does better on mineral soil 
or on moss, dead wood, or duff, is largely because so much depends 
upon the moisture conditions in the different materials. 
A plentiful supply of soil moisture is absolutely essential, not alone 
at the time of germination but throughout the period when the young 
plant is becoming established. This condition can be most readily 
obtained, and with the minimum amount of free moisture in the form 
of precipitation and seepage, under cover of the forest. That spruce 
will germinate and continue to grow and thrive on mineral soil can 
not be gainsaid, but only when such soil is protected from drying 
influences and is plentifully supplied with a constant amount of avail- 
able moisture at or very near the surface. The same applies to 
to needle litter and old logs . 
Needle litter when under a pure stand of spruce, particularly dense, 
unthinned, even-aged stands, is apt to accumulate much more rapidly 
than it will disintegrate. The upper layer forms a loosely compact 
mantle, which rapidly loses its surface moisture when exposed to 
drying influences. In the early spring or late fall, when humid con- 
ditions prevail, this mantle of needle litter contains sufficient moisture 
to induce germination, but the young plants are soon after destroyed 
by frost or drought. Furthermore, it is difficult for the young seed- 
lings to extend their root systems through the litter to mineral soil. 
In consequence, it is not suitable for a seedbed, and in fact, under 
such circumstances, is a great detriment to reproduction. ' If no great 
depth of such litter exists, so that the disintegrating humus layer is 
practically at the surface, the seedbed is admirable, since the humus 
is very retentive of moisture, and the vegetable mold full of nourish- 
ment. Acid humus, however, is not suitable, for though it is most 
common in supermoist situations it is physiologically dry. The same 
general considerations that apply to needle litter apply to a si ill 
greater extent to the leaf litter from hardwoods, since, particularly 
