The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1897-12-05
THE CAUSE OF PLANT COLORs.

The closing one of Professor Coulters
series of lectures on plant growth dealt in
an interesting way with the cause of color
in plants and flowers. The theory long
held by scientists was that the different
colors in plants were natures device for
attracting certain insects, which, by con-
tact with the plants, assisted in the work
of polarization. This was a pretty theory,
but it presupposed the ability in insects to
distinguish between colors, and a prefer
ence for one color over another. The latter
would be more difficult to account for than
the origin or object of colors. But Profess
sor Coulter says this theory is overthrown
by the discovery that many of the insects
which are known as poIlinators, or dis
tributors of plant pollen, are color blind
and therefore incapable of being attracted
to plants by their colors. His theory is,
and the Journal understands it to be a new
one, that the different coIors serve different
purposes in plant biology-that is in the
growth, development and nurture of the
plant Nothing is better known" he says,
than that the green color is for the pur-
pose of manipulating the light and that
by means of this manipulation certain of
the light rays are converted into other
forms of energy by the use of which the
protoplasm of the plant is able to assim-
ilate carbon-dioxide." Professor Jordan
thinks it equally certain that red, in all it's
forms and shades, extracts a certain degree
of heat from light and thus furnishes the
plant with a necessary element of it's life.
Illustrating this theory, he says:
The red flush of early spring buds seems
to suggest the need for greater heat at
that season. The reds of autumn leaves
which come just when the living substance
OF the leaf is ceasing it's work and retiring
into the stem, and hence is peculiarly
helpless, suggests a heat protection The
red algae, submerged deeper than any other
form OF marine vegetation, need greater
neat, both because of the chilling water
and on account of the diminished intensity
of the light passing through the water. The
reds of fruits may also be associated with
the greater development of heat which
may assist in those chemical changes which
occur in the process known as ''ripenng."
In this way 1t seems possible to associate
all the reds with the work of the plant in
its need of. greater heat.
This is fully as ingenious a theory as that
of the attraction of pollenizing insects by
colors, but yet it seems to be purely a the
Dry. 1t is the function of science to fur
nish facts rather than theories, and one
theory unsubstantiated by facts is not
worth much more than another. If the the
DRY that the red color furnishes heat to
plants be true, why are some plants sup
piled with so much more heat than others,
and many with none at all, and why are not
the plants which grow at great attitudes or
in high northern ATTITUDES not almost wholly
red? Many plants which bloom the year
round have no more red in winter than in
summer If the new theory is correct why
does nature. which gives all fur animals a
thicker coat in winter than in summer, and
in many other ways makes special provi-
sion against the cold-why does she not give
plants more red in winter than in summer?
The new theory does not seem to be ground
ed on facts.
All this speculation does not go to the root
of the matter. The question is not what
the different colors in flowers and plants
accomplish, but what causes them; not
what purpose they serve. but how they come
to be. AS theories are in order. suppose the
Journal advances one. Suppose we dismiss
the idea that colors in plants and flowers
serve any utilitarian or scientific purpose
whatever. and that they exist simply for
their own sake and to foster and satisfy
the love OK the beautiful. If colors in plants
must needs serve utilitarian purpose, why
not the colors of bird plumage or the in
finitely varied hues that fill the natural
world? Doubtless God could have made the