Plant Autographs and Their Revelations

This project is made possible by a grant from the Institute of Museum and Library Services as administered by the Pennsylvania Department of Education through the Office of Commonwealth Libraries The present volume gives a connected and popular account of the researches that have been carried out in the Bose Institute, one of the objects of which, as explained in the Appendix, is to associate the advancement of knowledge with the widest possible civic and public diffusion of it.

In pursuing investigations on the border region of physics and physiology, I was amazed to find boundary lines vanish¬ ing and points of contact emerge between the realms of the Living and Non-Living. Metals are found to respond to stimuli ; they are subject to fatigue, stimulated by certain drugs and ‘killed’ by poisons. Between inorganic matter at one extreme end and animal life at the other, there is spread out the vast expanse of the silent life of plants. The difficulty that thwarts the in¬ vestigator at every step arises from the fact that the interplay of life-action is taking place within the dark profundities of the tree, which our eyes cannot penetrate. In order to reveal the intricate mechanism of its life, it is necessary to gain access to the smallest unit of life, the ‘life-atom,’ and record its throbbing pulsation. When microscopic vision fails we have still to explore the realm of the invisible.

I have been able to make the dumb plant the most eloquent chronicler of its inner life and experiences by making it write down its own history. The self-made records thus made show that there is no life-reaction in even the highest animal which has not been foreshadowed in the life of the plant. I shall take my readers with me step by step as the wonders became gradually revealed to me through artificial organs of extraordinary sensitiveness by which alone the realm of the invisible could be explored. The barriers which

seemed to separate kindred phenomena will be found to have vanished, the plant and the animal appearing as a multiform unity in a single ocean of being. In this vision of truth the final mystery of things will by no means be lessened, but greatly deepened. It is not less of a miracle that man, circumscribed on all sides by the imperfections of his senses, should yet build himself a raft of thought to make daring adventures in uncharted seas. And in his voyage of discovery he catches an occasional glimpse of the ineffable wonder that had been hidden from his view. That vision crushes out of him all self-sufficiency, all that kept him unconscious of the great pulse that beats through the universe. The joy that fills my life I would wish to share with my readers.

The latent phase of life — Life-reactions in the realm of the invisible — Subtle impression left by external stimulation — Apparent difference between life-activities of plant and animal — Revela¬ tions of internal condition by response to questioning shock — Problem of essential unity in the responsivity of plant and animal ........... i Recording response of a dumb person — The sensitive Mimosa pudica — The Response Recorder — Stimulation by induction shock — Uniform responses — The Resonant Recorder — Sensitive and ordinary plants — Responsive contraction of ordinary plants —

The latent period of response — Effect of fatigue on latent period and on amplitude of response — Effect of a passing cloud — Motor paralysis under intense cold — Death under heat-stroke — Range and acuity of perception — Evolutionary differentiation of the physiological mechanism — Question of consciousness — Plant and animal behaviour ......... 17 Contractile mechanism in plant and animal — Active, semi-active and inactive motor organ — Motor reaction of pulvinus — Demarcation of muscular tissue by staining — Rapidity of reaction dependent upon presence of active substance^ — Effect of carbonic acid gas on response — Effects of Sulphuretted Hydrogen, Ether, Chloroform and Alcohol .......... 25

Method of obtaining electrical response — Quantitative mechanical stimulation — Uniform response — Fatigue — Effect of poison — Death under chloroform — Plant scalded to death . Test of sleeping and waking — The Sleep Recorder — Response at middle of the day — Gradual waking in the morning — Diurnal record of variation of sensibility ...... Morning and evening position of the tree — Periodic alternation of up and down movements — Record of diurnal movement — Explanation of the phenomenon — The Automatic Recorder — Characteristic autographs of different plants . . . .

Fatigue of detector for Wireless Waves — Restoration of sensibility after rest — Inertness from long passivity — Electric response of metal — Response enhanced by stimulants — Response ‘killed’ by poison — Living and Non-Living . . . . . The plant as a machine — The signal of death — Electrical discharge at death — Memory revival — The spasm of death — The Death Recorder — Transmission of death-excitation — Continuity be¬ tween life and death ........

Rhythmic pulsation of Telegraph plant — Automatic pulsation in animal and plant — Effects of change of internal pressure — Action of narcotics — Antagonistic reactions of poisons — Discovery of connecting link between ordinarily responding and automatically responding plants — Multiple response — Semi-automatism — Rhythmic sensation — Transient and persistent spontaneity Measurement of growth — The High Magnification Crescograph — Pulsation in growth — Effect of internal hydrostatic pressure — Effect of stimulation — Similarity of response of pulvinated and of growing organs — Effect of variation of temperature — Effect of anaesthetics — Effect of chemical stimulants — Effect of indi¬ rect and direct stimulation — The Law of the effect of Indirect and Direct stimulation — Modifying effect of tonic condition

The Balanced Crescograph — Record of effect of an instantaneous flash of light — Wireless waves and growth — Magnetic amplifica¬ tion of growth — Movements — Rejuvenescence — Life in a state of suspense .......... Effect of wound on growth — Pin-pricks and knife-wounds — Effect of thrashing on backward growth — Effect of wound on pulsating leaflets — Motor-paralysis caused by severe wounds Mechanical and photic stimulation — Geotropic irritation — Effect of temperature on geotropic reaction — Effect of ether — The statolith-theory — Localisation of the geo-perceptive layer by means of the Electric Probe — Sliding of starch-grains at critical inclination ........

Tropic movements — The twining of a tendril — Positive curvature — Effect of indirect stimulation — Bending away from stimulus . The ^leep and waking of the Water-Lily — Complexity of the problem — The process of elimination — Diurnal record of the Water-Lily — Movement of Cassia under variation of light Physical theories — Pull and push by the terminal organs — Propulsion of sap essentially due to vital activity — Effect of poison on the ascent of sap — Propulsion of blood in the animal — The leaf as an indicator of the flow of sap — The Electric Phytograph — Effect of alternate applications of chemical depressants and stimulants on ascent of sap — Effect of alternate application of cold and warmth ........

Searching for the ‘heart’ of the plant — Localisation of the pul¬ sating layer by the Electric Probe — Tests of heart-action — Effect of diminished and increased internal pressure on pulsation — Effect of sub-tonic condition^ — Effect of anaesthetics — Nor¬ mal and reversed peristaltic waves — Function of the wood The periodic ‘weeping’ — Hourly variation of sap-pressure — Pressure variation in leafless trees — Variation of pressure in leafy trees — Exudation from the Mango-tree — Discovery of the cause of the ‘weeping’ ........

Automatic Recorder for measurement of exudation — Hourly varia¬ tion in the yield of sap — Explanation of the greater exudation at night — Necessity for repeated wounding of Palm for exuda¬ tion of sap — The process of ‘milking’ the Palmyra Palm Record of the pulse-beat of the animal — The Plant Feeler — The Optical Sphygmograph — Pulse records under stimulants and depressants — Characteristic action of alkaloids — Effect of stimulants — Action of depressants — Antagonistic reactions — Stimulant-depressants — Action of Cobra-venom — Effect of Shuchikavaran on cardiac pulsation .

Automatic record of assimilation — The hourly variation of assimila¬ tion — Effect of infinitesimal traces of chemical substances — Efficiency of green plants in the storage of solar energy The ‘receptor,’ the ‘conductor’ and the ‘effector’ — Water-pipe or ‘nerve’ — The theory of sap-movement — Test for nervous im¬ pulse — Measurement of velocity of impulse — Arrest of impulse by physiological block — Polar excitation by electric current The Electric Probe for localisation of nervous tissue — Nerve-dis¬ tribution mapped out by effective staining — Experiments with isolated plant-nerve — The synaptic and synapsoidal membranes — t‘Bahnung’ or Facilitation — Cotton-wool treatment — The leaf as a catchment-basin of stimulus . . . . .

Opposite effects of moderate and intense stimulation— Basking in the sun-— Complexity of motor-organ of Mimosa— Rectilinear and torsional movements — Nerve-connection between leaf and pulvinus — The anchored moth ..... Reflex action in the animal — Reflex arc in Mimosa — Sensory and motor impulse — Effect of strychnine — The executive centre — ‘Lying low’ .......... The nerve-circuit — Problem of nervous control — Molecular trans¬ mission of impulse — Effect of molecular predisposition on nervous impulse — Power of directive control by the Will — Man victorious over circumstances ......

The Surge of Life — The Two Ideals — The Outlook — -Wider Synthesis The immense possibilities of life in the plant are at times latent and all but imperceptible. The gigantic Banyan tree exists potentially in a body smaller than a mustard seed. Within the enclosure of the seed-coat life lies long in a state of suspense, to be awakened at the proper season and under favourable conditions. Extraordinary is the power of resistance possessed by life in its latent phase. Seeds have been subjected to cold so intense that under its action air becomes liquefied and mercury solid; and yet, within the defensive armour of the seed-coat, life persists, resisting all dangers from outside. Storms and hurricanes scatter the living seeds. The coco-nut rides the waves till anchored safely in some island yet to be inhabited. In due season there commences a series of astonishing trans¬ formations; the latent life awakens, the seed-coat bursts asunder and growth begins. The seedling seems as if pos¬ sessed of faculties almost human. Place it upside down, yet the primary root bends down unerringly to pierce the earth for water, and the stem rises upward for light and air. The root winds its way underground, avoiding stones and obstacles. The stem bends towards the light, and tendrils twine around a support. Such visible movements are strik¬ ing enough. But within the unruffled exterior of the plant- body, there are other activities, energetic and incessant, which have hitherto escaped scrutiny. Until we can enter

into this realm of the invisible, the mystery of its life and its diverse manifestations will remain unsolved. The plant has always appeared to us very remote, because its life is so still and silent. In its apparent immobility and placidity the plant stands in strong contrast to the energetic animal with its reflex movements and pulsating organs. Yet the same environment which, with its chang¬ ing influences, so profoundly affects the animal, is also playing upon the plant. Storm and sunshine, the warmth of summer and the frost of winter, drought and rain — all these and many more come and go about it. What subtle impressions do they leave behind? Internal changes there must be; but our eyes have not the power to see them.

The life-activities of plants appear, at first sight, to be very different from those of animals. But if, in spite of the seeming differences, it could be proved that they are fundamentally similar, that would undoubtedly constitute a scientific generalisation of very great importance. It would then follow that the complex mechanism of the ani¬ mal machine that has baffled us so long, need not remain inscrutable for all times, since the intricate problems of animal life would naturally find their solution in the study of corresponding problems in the simpler vegetable life. It would mean the possibility of very great advance in the science of physiology, of agriculture, of medicine, and even of psychology.

We are still profoundly ignorant of the fundamental reactions which underlie the life of plants, for numerous are the difficulties which baffle the investigator. Such knowledge as we have consists of insufficient facts upon which contending and irreconcilable theories have been based. Under these circumstances the only clear path is that which leads us away from the din of disputation to follow the trail of fact. We must therefore abandon all our precon¬ ceptions and put our questions directly, insisting that the only evidence which can be accepted is that which bears the plant’s own signature.

mystical who declare that they can tell the character and disposition of any one simply by careful observation of his handwriting. Scepticism is permissible as to the authen¬ ticity of such claims ; yet there is no doubt that one’s hand¬ writing may be modified profoundly by conditions, physical and mental. There still exist at Hatfield House documents signed by Guy Fawkes. Those who have seen them declare that there is a sinister variation in these signatures. The crabbed and distorted characters of the last words Guy Fawkes wrote on earth as, in the dark hours of the morn¬ ing on which he was executed, he set his hand to the written confession of his crime, tell their own tale of what had transpired in the solitary hours of that fateful night.

If such is the revelation that may be unfolded to the critical eye by the lines and curves of a human autograph, perhaps the plant can be induced to give us its own auto¬ graph which would similarly reveal its internal condition. The only conceivable way of effecting this would be to obtain a record of the response of the organism to a ques¬ tioning shock. When an animal receives an external shock, it may answer in various ways ; if it has a voice, by a cry : if dumb, by the movement of its limbs. The external shock is the stimulus ; the answer of the organism is the response. If we can make the plant likewise give some perceptible answer in response to a shock, we can then judge of the condition of the plant by the character of the answer. When in an excitable condition, the feeblest stimulus will evoke an extraordinarily strong response ; in a depressed state even a strong stimulus evokes only a feeble reply; and lastly, when death overcomes life, there is an abrupt end of the power to answer at all.

So long as we are alive we respond in one way or another to the various shocks or stimuli of our environment. Stimulus falling on matter produces a molecular upset, causing excitation, and this upset is exhibited in various ways according to the instrument of expression. Let us look for a moment at the different effects which may be produced by the same electrical current acting on different instruments. Acting on one kind of recorder, it produces a movement; on another, say an electric bell, it produces sound; on still another, it causes a flash of light. In like fashion, a stimulus acting on living tissue may cause excita¬ tion which manifests itself in different ways, according to the different organs of expression.

Take first the familiar example of response by move¬ ment; a drop of boiling water falling on the hand causes the muscles to twitch and the hand to be withdrawn. The same thing is seen in the leaf of the sensitive plant Mimosa, which suddenly falls down when struck. Also under the excitation of touch, the open Dionaea leaf closes on the fly, its prey. Again, instead of this mechanical movement we may, as we shall see, have electrical movement in response to stimulus ; and a suitable electrical recorder, the galvanometer, shows an electrical twitch each time the living tissue is excited. And lastly, among the forms of response, we have sensation itself.

Sight is the characteristic response of the retina; hear¬ ing of the ear, and so on; and in sensation, different parts of the brain act as so many responding organs. For the purpose of investigation in the laboratory we may take, say, the eye of a frog, with its optical nerve connected with the galvanometer instead of with the brain. It will then be found that each time a flash of light falls on the retina, the galvanometer responds with a sudden deflection, just as specific reactions in the brain are perceived as sensations.

We thus see the possibility of obtaining some kind of record of the response of the plant, by which its internal condition and the changes of that condition may be revealed. In order to succeed in this, we have first to discover some compelling force that will make the plant give an answer¬ ing signal, mechanical or electrical; secondly, to supply a means for the conversion of these signals into an intelligible script ; and last of all, we have ourselves to learn the specific significance of this hieroglyphic.

In answering the question, then, as to whether there is an essential unity in the responsivity of plant and animal, we have first to find out whether sensitiveness is character¬ istic of only a few plants, or whether all plants and every organ of every plant are sensitive. We have then to com¬ pare the characteristic reactions of plant and animal under parallel conditions, in order to find whether the normal response and its modifications under changed conditions are similar in the two cases.

When an animal receives a blow, it does not respond immediately. A certain short interval elapses between the incidence of the blow and the beginning of the reply. This lost time is known as the latent period. The psycho-analyst learns more of his human patient from this pause than his patient can tell him in words. In the plant also a definite period elapses between the incident blow and the responsive twitch. Does this latent period undergo variation, as in the animal, with change in the internal or external condi¬ tions? Is it possible to make the plant itself write down for us this very short latent period?

Further, is the plant excited by the various irritants which excite the animal? Is this irritation local, or does it give rise to an impulse which travels through the length of the plant and causes movement at a distance? If so, at what rate does this impulse travel, and what are the conditions which increase the rate, and under what other conditions is the impulse retarded or arrested? Is it pos¬ sible to make the plant itself record the rate and its varia¬ tions ? Is there any resemblance between the nervous impulse in the animal and the excitatory impulse in the plant ?

The characteristic effects of various drugs are more or less well known in the case of the animal. Is the plant similarly susceptible to their action? Will the effect of poison change with the dose? Is it possible to counteract the effect of one poison by means of another which acts as an antidote? In the animal there are certain pulsating tissues such as that of the heart. Are there any such spontaneously beating tissues in the plant? If so, are the automatic pulsations

in the animal and in the plant affected by external condi¬ tions in a similar manner? And what is the real meaning of spontaneity or automatism? Growth furnishes us with the most important example of automatism. But the rate of growth in a plant is far below anything that we can directly perceive. How, then, is this growth to be magnified so as to be rendered instantly measurable? What are the variations in this infinitesimal movement under external stimulus of light, or of touch, or of the shock of the electric current? What changes are produced by giving or withholding water and by applica¬ tion of various drugs? Above all, what are the main con¬ ditions which stimulate or retard growth?