ere else the trees are mixed, and wherever the soil is favourable
the beech rapidly drives out the birch. The latter loses its branches at
the touch of the beech, and devotes all its strength to the upper part
where it towers above the beech. It may live long in this way, but it
succumbs ultimately in the fight--of old age if of nothing else, for the
life of the birch in Denmark is shorter than that of the beech. The
writer believes that light (or rather shade) is the cause of the
superiority of the latter, for it has a greater development of its
branches than the birch, which is more open and thus allows the rays of
the sun to pass through to the soil below, while the tufted, bushy top
of the beech preserves a deep shade at its base. Hardly any young plants
can grow under the beech except its own shoots; and while the beech can
nourish under the shade of the birch, the latter dies immediately under
the beech. The birch has only been saved from total extermination by the
facts that it had possession of the Danish forests long before the beech
ever reached the country, and that certain districts are unfavourable to
the growth of the latter. But wherever the soil has been enriched by the
decomposition of the leaves of the birch the battle begins. The birch
still flourishes on the borders of lakes and other marshy places, where
its enemy cannot exist. In the same way, in the forests of Zeeland, the
fir forests are disappearing before the beech. Left to themselves, the
firs are soon displaced by the beech. The struggle between the latter
and the oak is longer and more stubborn, for the branches and foliage of
the oak are thicker, and offer much resistance to the passage of light.
The oak, also, has greater longevity; but, sooner or later, it too
succumbs, because it cannot develop in the shadow of the beech. The
earliest forests of Denmark were mainly composed of aspens, with which
the birch was apparently associated; gradually the soil was raised, and
the climate grew milder; then the fir came and formed large forests.
This tree ruled for centuries, and then ceded the first place to the
holm-oak, which is now giving way to the beech. Aspen, birch, fir, oak,
and beech appear to be the steps in the struggle for the survival of the
fittest among the forest-trees of Denmark.

It may be added that in the time of the Romans the beech was the
principal forest-tree of Denmark as it is now, while in the much earlier
bronze age, repr