Orleans County monitor. [volume] (Barton, Vt.) 1872-1953, 1897-10-04
WHY AUTUMN Lea YES ARE
COLORED.

The casting of the leaf is not a sud
den and quick response to any single
change in environmental conditions,
but is brought about with a complex
interplay of processes begun days or
perhaps weeks before any external
changes are to be seen. The leaf is
rich in two classes of substances, one
of which is of no further benefit to it,
and another which it has constructed
at great expense of energy, and which
is in form of the highest possible
usefulness to the plant. To this class
belong the compounds in the proto-
plasm, the green color bodies, and
whatever surplus food may not have
been previously conveyed away. The
substances which the plant must needs
discard are in the form of nearly in
soluble crystals, and by remaining in
position in the leaf, drop with it to
the ground, and pass into that great
complex labratory of the soil where
by slow methods of disintegration
useful elements are set free, and once
again may be taken up by the tree
and travel their devious course
through root hairs along the sinuous
roots, and up through million celled
columns of the trunk, out through the
twigs to the leaves once more.
The plastic substances within the
leaf, which would be loss to the
plant if thrown away, undergo quite
a different series of changes. These
substances are in the EXTREMIST parts
of the leaf, and to pass into the plant
body must penetrate many hundreds
of membranes by diffusion into the
long conducting cells around the ribs
twigs and stems. The successful re-
treat of this great mass of valuable
matter is not a simple problem. These
substances contain nitrogen as part
of their compounds, and as a conse-
quence are very readily broken down
when exposed to the sunlight. In the
living normal leaf the green color
forms most effectual shield from the
action of the sun, but when the re-
treat is begun, one of the first steps
results in the disintregation of the
chlorophyll. This would allow the
fierce rays of the September sun to
strike directly through the broad ex-
panses of the leaf, destroying all
within were not other means provided
for protection. In the first place,
when the chlorophyll breaks down,
among the resulting substances form
ed is cynophyll (blue) which absorbs
manner as the chlorophyll. In addi-
ton, the outer layers of cells of the
leaf contain other pigments, some of
which have been masked by the chic
rophyll, and others which are formed
as decomposition products, SO that
the leaf exhibits outwardlY gor-
geous panoply of colors in reds, yell
lows, and bronzes that make up the
autumnal display. From the wild. riot
Of tints shown by a clump of trees or
shrubs, the erroneous impression
might be gained that the colors are
accidental in their occurrence. This
is far from the case, however. The
keynote Of color in any species is
constant, with minor and local varia-
tions. The birches are golden yell
low; oaks vary through yellow or
ange to reddish brown; the red maple
becomes dark red; the tulip tree
light yellow; hawthorn and poison
and vines take on flaming scarlet.
These colors exhibit some variation
in accord with the character of the
soil on which the plants stand. -Har-
pers.