PLANT INTELLIGENCE
“_The Marigold goes to bed with the sun,
And with him rises weeping._”--_Shakespeare_
It is no new thing to believe in the existence of intelligence among
plants. As far back as Aristotle, various great minds in the earth’s
history have ascribed definite, thinking acts to our floral and
vegetable friends. Not a few have seen unmistakable evidences of soul
in plantdom. Even the most skeptical have become aware of many things
they cannot explain in purely mechanistic terms.
We are still living in an age which has deified human wisdom. Man
has built up vast systems of knowledge and law, all based on his own
deep-rooted convictions. He approaches every subject with apriori
beliefs and presumptions. He is slow to acknowledge thinking powers to
his companion creatures of a terrestrial universe.
[Illustration: ALLIES OF THE DESERT ARM THEMSELVES WITH PRICKLES AND
THORNS AGAINST THEIR ANIMAL ENEMIES]
To a person on a country road, the wayside trees and flowers are
too often mere happenings or creations. Their ways are so quiet and
undemonstrative, that, if he has never been taught differently, he
rarely thinks of classifying them as independent, free-acting beings.
The fact that they are anchored to the soil seems to remove them from
the realm of self-willed creation. Yet why should it? Are fishes not
doomed to pass all their days in the chemical combination of hydrogen
and oxygen we call water? Does not the delicate Canary die if the air
surrounding it goes below a certain temperature?
The fact is that many plants exhibit all the elemental qualities of
human intelligence and also have vague psychic expressions of their own
which we only understand in a very limited way.
What causes the radicle or root of the smallest sprouting seedling
always to grow down and the plumule or stem always to grow up? It
cannot be gravity because that great earth pull would affect both parts
equally. This same radicle, when it has developed into a full-fledged
root, feels and pushes its way through the earth in a marvellous
fashion searching out water and traveling around obstructions with
unerring exactness. The slightest pressure will serve to deflect it;
aerial roots have been observed to avoid obstacles without actually
coming in contact with them. The plants use their roots to feel their
way to moisture and nourishment just as a man would feel his way with
his hands. The great Darwin, himself, wrote many years ago: “It is
hardly an exaggeration to say that the tip of the radicle thus endowed,
and having the power of directing the movements of the adjoining parts,
acts like the brain of one of the lower animals.”
In the same way, plant tendrils seek and search out the best supports,
after the manner of animal tentacles. When fully wound around a prop,
they drag the body of the plant up after them.
Practically all plants show a full knowledge of the importance of
sunlight to their life processes. They usually strain all their
energies and exert all their ingenuity in an effort to display as great
a leaf surface as possible. That this action is not always purely
instinctive is indicated by the response of certain carnivorous plants
to light. Having learned that success in capturing their prey depends
upon a static position of their leaves, they make no effort to adjust
their parts to strong or concentrated light. This is clearly a case of
intelligent adjustment to environment.
It is interesting to note that the plant cells which are sensitive to
light often become tired or partially blinded just like the retina of
an animal eye. Darwin found that plants kept in darkness were much more
responsive to light than those which dwelt habitually in the sunshine.
Many plants are wonderful weather prophets and keepers of time. Their
reactions to the coming of night, showers, heat, cold and other
natural phenomena show much wisdom. That plants require the rest which
accompanies sleep is indicated by the weakened and degenerate condition
of individuals which are sometimes forced to exceptionally rapid
development by continual exposure to electric light.
A human faculty which few people associate with plants, is an acute
sense of taste. How else do the plants know what elements to absorb out
of the soil? Certain experiments have enabled investigators to discover
marked taste preferences of a number of microscopic plants. Bacteria
are exceptionally fond of kali salts. Though they thrive equally well
on glycerine, they can be lured from it at any time by the toothsome
kali solution.
A sense of taste plays a remarkable part in the fecundation of Moss.
The male element is composed of swift-swimming cells equipped with
vibratory hairs. When deposited by the wind or other means on the cups
of the female flower, they swim about in the moisture until they are
eventually enticed to the unfertilized eggs at the bottom by their
taste for malic acid. That this is no idle theory can be proved in the
laboratory. The seed-animalcules of some of the Ferns also are urged to
the act of impregnation by their preference for the sugar in the seed
cups.
All through the plant world we see actions and habits which are the
reverse of automatism or mere instinctive response. Every plant
continually has to meet new and trying conditions, and while its
reactions, just like those of man, are frequently in the terms of
racial and individual experience, it is constantly called upon to make
new and novel decisions.
Consider the intelligence of a wild Service Tree described by
Carpenter. As a seed, it sprouted in the crotch of an Oak, and at once
sent a lusty root down toward the earth. As it descended the Oak trunk
and neared the ground, its further progress was barred by a large stone
slab. It is authentically recorded, that, when still one and one-half
feet away, the tip of the root, by direct perception or occult means,
discovered the presence of the obstruction, and, at once splitting into
two equal branches, passed on either side of the stone.
A more remarkable case is that of a tropical Monstera, which, coming
into life on top of a greenhouse, sent canny and vigorous roots
directly down to certain water tanks on the ground.
Isolated instances of plant intelligence might be mere coincidences if
it were not for the fact that they multiply greatly the further one
investigates. The common Potentillas and Brambles show remarkable
sagacity in searching out hidden veins of soil among the rocks where
they grow. Nothing is more ingenious than the way in which Hyacinths,
Primroses and Irises smother competitive seedlings by putting forth
large, low-lying leaves to cut off the light of neighbours.
Plants are great inventors, and by continual experimentation have
perfected thousands of ingenious devices to help them in their life
struggles. Many of these have to do with the all-important processes
of reproduction and cross-fertilization. The elaborate organs which
oftentimes force visiting insects to aid the flowers in their
love-making are conclusive proofs of directing intelligence. If, as is
generally believed, vegetable life preceded animal life on this planet,
then the plants must have developed these special reproductive organs
in which insects act as the fertilizing agents as direct attempts to
benefit the race by cross-breeding.
While cross-fertilization is vitally necessary for the maintenance of
a vigorous and hardy stock, inbreeding either between flowers of the
same plant or even between the organs of a single bi-sexual flower is
often practiced. In the love-making of the Grass of Parnassus and the
Love in the Mist (_Nigella_), we have a very pretty and intelligent
act. The flowers are unisexual and, as the females usually grow on
much longer stalks than the males, the latter would not have much
chance of showering their pollen on their consorts, if it were not for
the fact that, at the proper season, without outside stimulation, the
“tall females bend down to their dwarf husbands.” This surely is as
intelligent and conscious as the mating of animals.
The carnivorous plants act with uncanny wisdom. The insect-devouring
Sundews pay no attention to pebbles, bits of metal, or other foreign
substances placed on their leaves, but are quick enough to sense the
nourishment to be derived from a piece of meat. Laboratory specimens
have been observed to actually reach out toward Flies pinned on cards
near them. So highstrung are these sensitive organisms that they can
be partially paralyzed if certain spots on their leaves are pricked.
Many people have no hesitancy in ascribing considerable intelligence
to the higher animals; why do they balk at making the same concession
to plants? If you concede intelligence to a single animal, you
concede _some measure_ of brain-power to all animals down to the
one-celled Amoeba, and so must grant the same favour to the plant
world. Plants and animals, besides having many habits in common,
in their simplest forms are often indistinguishable. Both reduce
themselves to single-celled masses of protoplasm. The Myxomycetes are
both so plant-like and at the same time so animal-like that their
classification “depends rather on the general philosophical position of
the observer than on facts.” Possibly they are both animal and plant at
the same time--a sort of “missing link” connecting the two kingdoms of
life.
Anent the same question Edward Step says, “Modern thought denies
consciousness to plants, though Huxley was bold enough to say that
every plant is an animal enclosed in a wooden box; and science has
demonstrated that there is no distinction between the protoplasm of
animals and plants, and that if we get down to the very simplest forms
in which life manifests itself we can call them animals or plants
indifferently.”
When one considers the rooted, plant-like life of Mollusks and Hermit
Crabs, and then the active, animal-like life of the free-swimming Moss
spores and the wind-borne Fungi, he is tempted to wonder if, after all,
this talk of plants and animals, is not just another of man’s arbitrary
classifications, which may be superceded in time by some other system
of nomenclature.
Of only one thing are we sure, and that is that all life is one--an
expression of the intelligence and power which pervades the universe.
Many readers may vaguely feel and believe these facts and yet not be
certain that plants are individually and personally intelligent; long
training makes them still feel that the many admittedly clever and
ingenious acts recorded every day in plantdom are but the indications
of some external mind or force working through Nature. The plants act
in certain ways because they have no choice in the matter; they are
passive tools in the hands of such craftsmen as “instinct,” “heredity,”
and “environment.” The answer to this is that you can ascribe an
exactly similar fatalistic interpretation to every human thought, word
or deed. What you consider the freest decision of will you made today
can be shown conclusively to be the result of a long train of acts and
influences which stretches back to Adam. It would have been impossible
for you to have acted differently.
Such blanket reasoning leads nowhere. If you believe that you are a
free, independent, decision-making soul (and who does not?) logically
you must grant the same rights to the humble Squash.
Even in the terms of man’s own science, the plants can be shown to be
intelligent. The psychologist Titchner classifies the three stages of
mental processes as (1) Sensations (2) Images and (3) Affections. The
term “affection” is here used in the special sense of a capacity for
entering into intellectual states of pleasure or pain.
In view of what has already been said, it hardly seems necessary to
prove the existence of sensation in plants. The very fact that all life
is a constant response to stimuli and the adjustment to environment
presupposes the existence of plant sensation. Only a few hours passed
in the investigation of plant habits will show our vegetable friends
giving definite responses to heat, cold, moisture, light, and touch,
while laboratory experiments show their sensitive powers of taste and
hearing.
The touch sense of the Sundew is developed to such an extent that it
can detect the pressure of a human hair one twenty-fifth of an inch
long. The tendrils of the Passion Flower attempt to coil up at the
slightest contact of the finger and as quickly flatten out upon its
removal. The stamens of the Opuntia or Prickly Pear have specialized
papillae of touch exactly similar to the papillae of the Hermione Worm.
When rubbed by the body of an insect, they transmit an impulse which
causes the anthers to let loose a shower of pollen on the intruder.
The animal world cannot exhibit a higher sensitiveness to touch than
that displayed by the celebrated Venus Fly-Trap. On each side of the
leaf midrib stand three sharp little bristles. They are the sense
organs controlling the closing of the vegetable spring. Quick must an
insect be to escape their vigilance.
Sensation and imagery are so closely connected in the human brain that
the existence of one would seem to predicate the other. Fortunately, we
have very good evidence to indicate the faculty of plant memory, which
must necessarily be built up of images of one kind or another.
If a plant which is accustomed to folding its leaves together in sleep
on the setting of the sun, be placed in a completely dark room, it
will continue to decline and elevate its foliage at regular intervals,
indicating that it remembers the necessity for rest even with the
reminder of outside stimuli lacking.
By what faculty do plants become aware of the approach of spring?
Only occasionally are they deceived by January thaws, and no matter
how unseasonably cold a March may be, they go right ahead with the
preparation of April buds and leaves. So accurate is plant knowledge
about the seasons that Alpine flowers often bore their way up through
long-lingering snow, even developing heat with which to melt the
obstruction, when they feel that spring has really come. What gives
plants such courage in the face of contradicting elements, if not an
accurate sense of the passage of time and therefore the memory of other
seasons, which implies imagery?
Until we develop a workable system of thought communication with
plants, we can never scientifically prove that plants are capable
of psychological “affections” or emotions. Mental states are purely
personal matters. We would never be sure that any other human being
went through feelings of love, anger, hate and pity, similiar to our
own, if he were not able to tell us of them. Until the plants can
describe to us their inner emotions, we can never definitely know
whether they have real feelings, and if they parallel the human variety
in any degree. But just as we have become able to read a man’s mental
processes by his facial expressions, tone of voice and bodily posture,
so we can guess at plant emotion by external manifestations. When a
flower greets the morning sun with expanded petals, uplifted head and
a generally bright appearance, why should we not say it is happy and
contented? When an approaching storm causes a plant to droop its body
and contract its petals and leaves into the smallest compass possible,
why is not fear, apprehension and melancholy indicated? When the jaws
of the Venus Fly-Trap close on its hapless victim, they must do so with
a savage joy akin to that of a Tiger springing on its prey.
There are those who relegate a certain amount of intelligence to plants
but deny them consciousness. They are unwilling to admit that plants
are aware of their own physical and mental processes. This would
seem to be the merest quibbling over terms and an entrance into that
metaphysics which does away with all consciousness.
If plants were not conscious, at least under stimulation, they would
have long since perished from the earth through inability to react to
new conditions. Francis Darwin says: “We must believe that in plants
exists a faint copy of what we know as consciousness in ourselves.”
Many scientists believe that life and consciousness always precede and
are superior to organization. It is urged that possibly many plants
possess consciousness without self-consciousness or introspection.
After a thoughtful consideration of such facts as these, only the
blindest prejudice can continue to laugh at plant intelligence. Why
then has the world of human thought been so long and reluctant to
acknowledge it? Simply because it always reasons along authentic and
established lines. For many years it has been taught to associate
animal movement with special groups of cells called muscles and
intelligence with special groups of cells called nerve tissue. Failing
to find any trace of nerve tissue in plants, it ignores a hundred
convincing facts to the contrary, and declares that plant intelligence
is a myth. Failing to detect a _mechanism_ of sensibility, it denies
the existence of sensibility, even though in the little Mimosa the
sense of touch travels from leaf to leaf before our eyes.
It must be realized that the animal brain merely acts as the electrical
motor for the life-power which drives the universe. This motor and all
of its auxiliaries are absent in Protozoa and other one-celled animals,
but the power is not. In the same way, they are absent throughout all
plantdom, but the eternal life principle manifests itself in many
mighty acts.
What is a nervous system, anyhow? It is a group of cells, the
specialized function of which is to transmit impulses from one to
the other by certain obscure chemical reactions. Why cannot ordinary
tissue cells do the same thing, possibly in a feebler, less efficient
way? Plant cells are all joined together by fine connecting strands,
forming a “continuity of protoplasm” through which such impulses could
readily travel. Whether investigators agree to this or not, it is an
indisputable fact that it is true.
Though science is now beginning to verify the fact of plant
intelligence most conclusively great and independent thinkers of all
times have long felt its truth. Certain minds are always in advance
of their age. While science laboriously proves every step of its way
with painstaking and commendable exactness, they are soaring far ahead
in new and fascinating fields. Sometimes they go astray, but quite as
frequently they are the pioneers of great and progressive ideas.