their roots for moisture in the soil, and for light
and space by the growth of their crowns in height and breadth. Perhaps
the strongest weapon which trees have against each other is growth in
height. In certain species intolerant of shade, the tree which is
overtopped has lost the race for good. The number of young trees which
destroy each other in this fierce struggle for existence is prodigious,
so that often a few score per acre are all that survive to middle or old
age out of many tens of thousands of seedlings which entered the race of
life on approximately even terms.

Not only has a forest a character of its own, which arises from the fact
that it is a community of trees, but each species of tree has peculiar
characteristics and habits also. Just as in New York City, for example,
the French, the Germans, the Italians, the Hungarians, and the Chinese
each have quarters of their own, and in those quarters live in
accordance with habits which distinguish each race from all the others,
so the different species of pines and hemlocks, oaks and maples prefer
and are found in certain definite types of locality, and live in
accordance with definite racial habits which are as general and
unfailing as the racial characteristics which distinguish, for example,
the Italians from the Germans, or the Swedes from the Chinese.

The most important of these characteristics of race or species are those
which are concerned with the relation of each to light, heat, and
moisture. Thus, a river birch will die if it has only as much water as
will suffice to keep a post oak in the best condition, and the warm
climate in which the balsam fir would perish is just suited to the
requirements of a long leaf pine or a magnolia.

The tolerance of a tree for shade may vary greatly at different times of
its life, but a white pine always requires more light than a hemlock,
and a beech throughout its life will flourish with less sunshine or
reflected light than, for example, an oak or a tulip tree.

Trees are limited in their distribution also by their adaptability, in
which they vary greatly. Thus a bald cypress will grow both in wetter
and in dryer land than an oak; a red cedar will flourish from Florida to
the Canadian line, while other species, like the Eastern larch, the
Western mountain hemlock, or the big trees of California, are confined
in their native localities within extremely narrow limits.

THE FORESTER'S KNOWLEDGE

The