THE NATURAL REGENERATION OF WOODS. 67 
the overhead shading ; in the latter there is no vertical shade or 
shelter, though there is usually lateral protection. The former of 
these two cases in its various modifications being the more import- 
ant, may be taken first. 
The regeneration of a forest on a shelter-wood system may be 
accomplished in various ways, the most common being that where 
the whole is taken in hand at one time, that is to say, the several 
processes or stages in the operation of natural regeneration proceed 
simultaneously throughout the whole wood. 
When it has been resolved to renew a wood by natural seeding, 
all efforts must be directed towards providing conditions which will be 
likely to bring about a successful result. It comparatively seldom 
happens that the surface of the ground is naturally in a proper 
state to receive the seed, and that the number and distribution of 
the trees over the area are such as to secure the proper conditions as 
regards light for the health and development of the young seed- 
lings. It therefore becomes necessary, afew years before the actual 
shedding of the seed is to be expected, to undertake various pre- 
liminary operations in order to avert as much as possible the chances 
of failure. If the closeness of the wood is such that no weeds, but 
only dead leaves and twigs, cover the surface of the ground, this 
preparatory stage offers but few obstacles. It is then only neces- 
sary to make several very moderate fellings in order to hasten the 
decomposition of the raw humus, and to bring about a perfectly 
regular distribution of the old trees, so that every part of the ground 
may receive the necessary supply of seed, and at the same time be 
equally shaded. At first attention should chiefly be directed 
towards removing the smaller class of trees, namely, those that are 
overgrown, diseased, or poorly developed, and therefore not likely 
to bear much seed, as well as those species which it is not desir- 
able to have represented in the next generation. If we are dealing 
with a mixed wood, the fellings should also be directed towards 
proportioning the trees as they are intended to be represented in 
the young wood, due regard being taken of the fact that some 
species produce far more seed than others, and that some seeds, 
especially those provided with wings, possess special facilities for 
distribution. 
The advance fellings may take only one or two years to accom- 
plish, or as many as ten or fifteen if the wood is situated ina region 
subject to heavy gales, or if the trees are of a shallow-rooted species, 
for in these cases the process of thinning must be very slowly 
