The daily banner. (Cambridge, Md.) 1897-2008, 1917-10-29
Why The Leaves
Change Their Color

Washington. Oct. 24.-lt requires
no vivid imag aginatiOn to picture Mo
ther Nature going about these days
with a liberal supply of paint with
which she colorS the leaves of the
trees aad other plants and thereby
produces the vivid tints which char
acterize the foliage Of this season. In
reality the change in cOloring Is the
result nf certain chemical processes
W hich take place in the leaves.
The change is not, as many peo-
pie suppose, due to the action of
frost, bat is preparation for winter
All duiing the spring and summer
the lea yes have served as factories.
where the foods necessary for the
trees growth have been manufacture
ed. This food making takes place in
numbeiless tiny cells of the leaf, and
is carr ed on by small green bodies.
which eiye the leaf its color. These
chlorot hyll bodies, as they are
knoSa ks the food of the tree by
combining carbon taken from the
carbonio acid gas OF the air with
hydrogen, oxygen, and various min
erals supplied by the water which
the roots gather. In the fall when
the cool weather causes a slowing
down OF the vital processes, the
work of the leaves comes to an end.
The machinery of the leaf factory is
dismantled, so to speak, the chloro-
phyll is broken up into the various
substances of which it is composed.
and whatever food there is on hand
is sent to the body of the tree to be
stored up for use in the spring. All
that remains in the cell cavities of
the leaf is a watery substance in
which a few oil globules and crys-
tails, and small number of yellow.
strongly refractive bodies can be
seen. These give the leaves the yell
low coloring so familiar in autumnal
foliage
1t often happens. however, that
there is more sugar in the leaf than
can be readily transferred back to
the tree. When this is the case the
chemical combination with the other
substances produces many-colored
tints varying from the brilliant red
of the dogwood to the more austere
red-browns of the oak. In coniferous
trees, which do not lose their foliage
in the fall, the green coloring matter
which, however, gives way 10 the
lighter color in the spring.
While the color of the leaf is
changing, other preparations are be
ing made. At the point where the
stem of the leaf is attached TO the
tree, a special layer of cells develops
which gradually sever the tissues
which support the leaf. At the same
time Nature heals the cut, so that
when the leaf is finally blown Off by
the wind or falls from its own
weight, the place where it grew on
the twig is marked by a soar.
Although the food which has been
prepared in the cell cavities is sent
back to the tree. the mineral sub
stances with which the walls Of the
cells have become impregnated dur
ing the summer months are retained.
Accordingly. when the leaves fall
they contain relatively large amounts
of valuable elements. such as nitro
gen and PHOSPHORUS which were
originally part of the soil. The de-
composition of the leaves results in
enriching the top layers OF the soil
by returning these elements and by
the accumulation of humus. That is
why the mellow black earth from the
forest floor is 80 fertile. But if fires
are allowed 10 run through the for
est and the leaves are burned, the
most valuable of the fertilizing ele-
ments are changed by the heat INTO
gases and escape into the air. As a
result. forests which are burned ov-
er regularly soon lose their soil fer
tility even if no apparent damage is
done 10 the standing timber.