Evening star., 1901-10-29
THE HUES OF AUTUM N
GENERAL DISCUSSION OF THE
COLORS OF LEAVES.
Possible to Have Autumn Leaves in
Other SeasOns-TObacco often
Changed.

A paper read recently by Albert +. WOODS
of the division of vegetable physiology and
pathology, Department of Agriculture, on
the forbidding subject ''The Destruction of
Chlcrophyll by Oxidizing Engines" COM
bined with the unusually luxuriant and
brilliant foliage of the current fall, has
given rise to much discussion of the chem
ical process which occasions the change in
leaf colors during the period of frost. Mr..
Woods has been besieged with letters of
inquiry and inquiries made in person. His
supply of the pamphlet with the obscure
title is practically exhausted, but there is
no apparent escape from further search for
information.
According to the botanies the change of
color is due to a very simple process of
fermentation. A chemical compound known
as "chlorophylI' is found In the cells Of
every leaf and this substance, when fer
this statement, according to the latter-day
authorities of the Agricultural Department,
is only approximately true.
One commentator on the subject who
sought to state the chemical process for the
benefit Of the layman did so in the follow
ing words:
Light frosts, not sufficient to kill leaves.
greatly facilitate their coloration by caus-
ing an increase within them of a normal
chemical ferment, which attacks the color
compounds or color generators In the cells.
1t is the oxidation of these color COM
pounds by this ferment that produces the
various shades Of color, especially the pur-
pies, oranges, etc. The yellows are normal
ly in the leaf. The primary principle of this
chemical action Is that all the colorS of
which a particular leaf is capable are in
the leaf as 1t hangs upon the tree in sum-
mer. and that 1t is the withdrawal of some
Of the elementary colors that transforms
the leaf to its autumn hue"
A Long Fall Required.
Mr.. Woods has been quoted as making
the following comment on the subject:
Autumn leaves containing sugar, such
as the naples, sumachs. gums, ETC., easily
oxidize, and thus form the rich reds, pur-
pies and violets so beautiful to the eye.
That is why these especially the hard ma
pies give the most beautiful autumn leaves
Autumnal oak leaves do not attract admi-
ration because they contain much tannin.
The oxidation color of tannic acid is dirty
brown. Leaves which die quickly never
give autumnal colors The most gorgeous
autumn leaves are produced by long
drawn-out fall, whose days gradually cool
from summer heat to winter snow. Put
If the frost should come early and the
weather should be uneven, we need not
expect the true autumnal splendors. A
heavy, sudden and early frost would kill
all leaves alike and turn them to a mo-
notonous brown.
Although couched in scientific phraseol-
ogy, Mr.. Woods paper is comprehensive
by almost every one when the word en-
lyme is defined. An engine or enzym is
substantially only a leaven, particle that
causes fermentation 1t is more accurately
designated IAN unorganized or chemical
compound Of vegetable or animal origin
that causes fermentation" Mr.. Woods
essay is thus paper on THE Destruction
of the Green Color in Plants by Oxidizing
the Particles of Leaven.'
The View of the Scientist.
- Ill a.
says:
"It has long been known that chlorophyll
could be readily converted by oxidation into
yellow coloring matter, exanthophyll So
Iutions of chlorophyll exposed TO light soon
lose their color. So far as 1 know, how
ever no one has observed any relation be-
tween oxidizing engines and these pro-
cesses of decoloration.
'It thus seemed likely that oxidizing en-
zymes which are widely distributed in
plants might take part in the autumnal
destruction of chlorophyll and also in cer-
tain diseases where the destruction of the
chlorophyll is a prominent feature and
where 1t Is known not to be due to the alb
sence of iron or lime.
q have found that hard maple leaves
and leaves of tobacco, both of which con-
tain oxidiZing engines, retain their color,
even when exposed to moderately strong
light, for long periods of time (three to four
days when moist, and Indefinitely when
dry), provided that the leaves are first
steamed for two. or three minutes or i'm
mersed in boiling water until it Is shown by
proper tests that the oxidizing engines are
destroyed
Changing Tobacco Leaves.
Spotted tobacco leaves have an extra
value to the cigarmaker for use as Su-
matra wrappers. In view of that consider
alton the following comment on Mr.. Woods
ability to produce that effect at will is of
particular interest:
"It is true that whole plants may be Of
lighter shade of green and apparently
healthy. Others, however. are of deeper
er than the lighter colored ones and con-
tain less peroxidase. We must therefore
look upon the lighter colored, weaker grow
ing plants and tissues as diseased and COM
parable to the lighter colored areas Of
other variegated leaves. There seems to be
no good reason for separating this disease
of tobacco from true variegation or albin-
ism 1t is favored by the same conditions
which favor variegation in other plants
namely, unsuitable soil nourishment, and
very moist soil with little light, accom-
panied by atmospheric conditions stimulat-
ing rapid growth. 1t is especially favored
by poor or weak Seed
Il have been able to produce the disease
at will In the following manner: Strong,
healthy plants, which had about used up
the -nourishment In the pots in which they
were grown. and which were approaching
the fruiting stage, were cut back to within
six to ten inches of the ground. leaving
only two of three of the lower leaves. Sew
eral buds Immediately started. but only one
or two were allowed to remain. The plants
were kept copiously watered at high tenn
perature and were slightly shaded The
young shoots grew very rapidly, and were
invariably mottled aud often distorted ex-
actly as in the mosaic disease. On the
other hand. plants cut back while they
were not making vigorous growth pro-
duced slower growing but healthy suckers.