Burlington weekly free press. [volume] (Burlington, Vt.) 1866-1928, 1917-12-20
WHY LEAVES
CHANGE COLOR.
Duo to Certain Chemical Processes and
Not to Frost.

Duo TO certain Chemical Processes ana
Not to Frost.
Il requires no vivid imagination to pic
ture Mother Nature going about in early
fall with liberal supply Of paint with
which she colors the leaves Of the trees
and other plants and thereby produces
the vivid tints which characterize the
foliage Of that season. In reality the
change in coloring is the result Of GER
tain chemical processes which take place
in the leaves.
The change Is not as many people sup
pose. due to the action of FROST but is
a preparation for winter. All during the
spring and summer the leaves have serv-
ed as factories. where tn foods necessary
for the tree growth have been manufac-
tured. This food making takes place in
numberless tiny cells Of the leaf and is
carried on by small green bodies which
give the leaf its color These chloro-
phyll bodies as they are known. make the
food of the tree by combining carbon
taken from the carbonic acid gas of the
air with hydrogen, oxygen, and various
minerals 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
speak, the chlorophyll is broken up into
the various substances of which 1t is
composed, and whatever food there is on
hand is sent to the body Of the tree to
be stored for use in the spring. All that
remains in the cell cavities of the leaf
IL a watery substance in which few
oil globules and crystals. and a small
number Of yellow, strongly retroactive
bodies can be seen. These give the
leaves the yellow 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 combina-
ton with the other substances pro-
duces many-colored tnts 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 takes on slightly brownish
tinge, which. however, gives way to the
lighter color In the spring.
While the color of the leaf Is changing,
other preparations are being made. At
the point where the stem of the leaf Ia
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
I place where 1t grew on the twig Is mark
cd by a scar.
b Although the food which has been pre-
pared In the cell cavities il sent back to
the tree. the mineral substances with
j which the walls of the cells have be.
come impregnated during the summer
months are retained. Accordingly. wher
the leaves fall they contain relatively
large amounts of valuable elements, such
rs nitrogen and phosphorus which were
2 originally part of the soil. The de.
composition of the leaves results In en-
I riching the top layers of the soil by re-
turning these elements and by the &C
emulation of humus. That is why the
mellow black earth from the fores
floor IL 80 fertile. But IL fires are allow
ed to run through the forest and thu
leaves are burned the most valuable o.
the fertilizing elements are changed b,
q the heat into gases and escape into tn,
air. AS result. forests which ar,
burned over regularly soon lose theil
= Esl fertility even II no apparent damag,
, - done to the standing timber.