Part 8

We might therefore have detected the internal condition of the plant, if, by some inducement, we could have made it write down its own responses. If we could once succeed in this apparently impossible task we should still have to learn the new language and the new script. In a world of so many different scripts, it is certainly undesirable to introduce a new one! I fear the Uniform Script Association will cherish a grievance against us for this. It is fortunate however that the plant-script bears, after all, a certain resemblance to the Devanagari--inasmuch as it is totally unintelligible to any but the very learned!

But there are two serious difficulties in our path; first, to make the plant itself consent to give its evidence; second, through plant and instrument combined, to induce it to give it in writing. It is comparatively easy to make a rebellious child obey: to extort answers from plants is indeed a problem! By many years of close contiguity, however, I have come to have some understanding of their ways. I take this opportunity to make public confession of various acts of cruelty which I have from time to time perpetrated on unoffending plants, in order to compel them to give me answers. For this purpose, I have devised various forms of torment,--pinches simple and revolving, pricks with needles, and burns with acids. But let this pass. I now understand that replies so forced are unnatural, and of no value. Evidence so obtained is not to be trusted. Vivisection, for instance, cannot furnish unimpugnable results, for excessive shock tends of itself to make the response of a tissue abnormal. The experimental organism must therefore be subjected only to moderate stimulation. Again, one has to choose for one's experiment a favourable moment. Amongst plants, as with ourselves, there is, very early in the morning, especially after a cold night, certain sluggishness. The answers, then, are a little indistinct. In the excessive heat of midday, again, though the first few answers are very distinct, yet fatigue soon sets in. On a stormy day, the plant remains obstinately silent. Barring all these sources of aberration, however, if we choose our time wisely, we may succeed in obtaining clear answers, which persist without interruption.

It is our object, then, to gather the whole history of the plant, during every moment between its birth and its death. Through how many cycle of experience it has to pass! The effects on it of recurring light and darkness; the pull of the earth, and the blow of the storm; how complex is the concatenation of circumstances, how various are the shocks, and how multiplex are the replies which we have to analyse! In this vegetal life which appears so placid and so stationary, how manifold are the subtle internal reactions! Then how are we to make this invisible visible?

THE DIARY OF THE PLANT.

The little seedling we know to be growing, but the rate of its growth is far below anything we can directly perceive. How are we to magnify this so as to make it instantly measurable? What are the variations in this infinitesimal growth under external shock? what changes are induced by the action of drugs or poisons? will the action of poison change with the dose? Is it possible to counteract the effect of one by another?

Supposing that the plant does not give answers to external shock, what time elapses between the shock and the reply? Does this latent period undergo any variation with external conditions? Is it possible to make the plant itself write down this excessively minute time-interval?

Next, does the effect of the blow given outside reach the interior of the plant? If so, is there anything analogous to the nerve of the animal? If so, again, at what rate does the nervous impulse travel the plant? By what favourable circumstances will this rate of transmission become enhanced, and by what will be retarded or arrested? Is it possible to make the plant itself record this rate and its variations? Is there any resemblance between the nervous impulse in plants and animals? In the animal there are certain automatically pulsating tissues like the heart. Are there any such spontaneously beating tissues in a plant? What is the meaning of spontaneity? And lastly, when by the blow of death, life itself is finally extinguished, will it be possible to detect the critical moment? And does the plant then exert itself to make one overwhelming reply, after which response ceases altogether? Its autobiography can only be regarded as complete, if, with the help of efficient instruments, all these questions can be answered by it, so as to form the different chapters.

"If the plant could have been made thus to keep its own diary, then the whole of its history might have been recovered!" But words like these are born of day dreams merely. Vague imaginings of this kind may furnish much gratification to an idle life. When, awaking from these pleasant dreams of science, we seek to actualise the conditions imposed by them, we find ourselves face to face with a dead wall. For the doorway of nature's court is barred with iron, and through it can penetrate no mere cry of childish petulance. It is only by the gathered force of many years of concentration, that the gate can be opened, and the seeker enter to explore the secrets that have baffled him so long.

DIFFICULTIES OF RESEARCH IN INDIA.

We often hear that without a properly equipped laboratory, higher research in this country is an absolute impossibility. But while there is a good deal in this, it is not by any means the whole truth. If it were all, then from these countries where millions have been spent on costly laboratories, we should have had daily accounts of new discoveries. Such news we do not hear. It is true that here we suffer from many difficulties, but how does it help us, to envy the good fortune of others? Rise from your depression! Cast off your weakness! Let us think, "In whatever condition we are placed, that is the true starting-point for us." India is our working-place, and all our duties are to be accomplished here, and nowhere else. Only he who has lost his manhood need repine.

In carrying out research, there are other difficulties, besides the want of well-equipped laboratories. We often forget that the real laboratory is one's own mind. The room and the instruments only externalise that. Every experiment has first to be carried out in that inner region. To keep the mental vision clear, great struggles have to be undergone. For its clearness is lost, only too easily. The greatest wealth of external appliances is of no avail, where there is not a concentrated pursuit, utterly detached from personal gain. Those whose minds rush hither and thither, those who hunger for public applause instead of truth itself, by them the quest is not won. To those on the other hand, who do long for knowledge itself, the want of favourable conditions does not seem the principle obstacle.

In the first place, we have to realise that knowledge for the sake of knowledge is our aim, and that the world's common standard of utility have no place in it. The enquirer must follow where he is led, holding the quiet faith that things which appear to-day to be of no use, may be of the highest interest to-morrow. No height can be climbed, without the hewing of many an unremembered step! It is necessary, then, that the enquirer and his disciples should work on ceaselessly, undeterred by years of failure, and undistracted by the thunder of public applause. We may one day come to realise that India in the past has shared her knowledge with the world, and we may ask ourselves, is that destiny now ended for us? Are we of to-day to be debtors only? Perhaps when we have once felt this, a new Nalanda may arise.

THE PHYTOGRAPH

I was speaking of the need of various delicate instruments--phytographs, as I shall call them--for the automatic record of the plant's responses. What was, ten years ago, a mere aspiration, has now after so many years of effort, become actual fact. It is unnecessary to tell here of many a fruitless and despairing attempt. Nor shall I trouble you with any account of intricate mechanism. I need only say that with the aid of different types of apparatus, it is now possible for all the responsive activities of the plant to be written down. For instance, we can make an instantaneous record of the growth and its variations, moment by moment. Scripts can be obtained of its spontaneous movement. And a recording arm will demarcate the line of life from that of death. The extreme delicacy of one of these instruments will be understood, when it is said that it measures and records a time-interval so short as one-thousandth part of a second!

It has been supposed that instruments for research of this delicacy and precision, were only possible of construction in the best scientific manufactories of Europe. It will therefore be regarded as interesting and encouraging to know that every one of these has been executed entirely in India, by Indian workmen and mechanicians.

With perfect instruments at our disposal, we may proceed to describe a few amongst the many phenomena which now stand revealed. But before this, it is necessary to deal briefly with the superstition that has led to the division of plants into sensitive and insensitive. By the electrical mode of investigation, it can be shown that not only Mimosa and the like, but all plants of all kinds are sensitive, and give definite replies to impinging stimuli. Ordinary plants, it is true, are unable to give any conspicuous mechanical indication of excitement. But this is not because of any insensitiveness, but because of equal and antagonistic reactions which neutralise each other. It is possible, however, by employing appropriate means, to show that even ordinary plants give mechanical replies to stimulus.

THE DETERMINATION OF THE LATENT PERIOD

When an animal is struck by a blow, it does not respond at once. 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. In the leg of a frog, the latent period according to Helmwoltz, is about one-hundredth of a second. This latent period, however, undergoes appropriate variation with changing external conditions. With feeble stimulus, it has a definite value, which, with an excessive blow, is much shortened. In the cold season, it is relatively long. Again, when we are tired our perception time, as we may call it, may be greatly prolonged. Every one of these observations is equally applicable to the perception time of the plant. In Mimosa, in a vigorous condition, the latent period is six one hundredth of a second, that is to say, only six times its value in an energetic frog! Another curious thing is that a stoutish tree will give its response in a slow and lordly fashion, whereas a thin one attains the acme of its excitement in an incredibly short time! Perhaps some of us can tell from our own experience whether similar differences obtain amongst human kind or not? The plant's latent period in our cold weather may be almost doubled. Ordinarily speaking it takes Mimosa about fifteen minutes to recover from a blow. If a second blow be given, before the full recovery of its equanimity, then the plant becomes fatigued, and its latent period is lengthened. When over-fatigued, it may temporarily lose its power of perception altogether, what this condition is like, my audience is only too likely to realise, at the end of my long address!

THE RELATION BETWEEN STIMULUS AND RESPONSE

According to varying circumstances, the same blow will evoke responses of different amplitudes. Early in the morning, after the prolonged inactivity of a cold night, we find the plant inclined to be lethargic, and its first answers correspondingly small. But as blow after blow is delivered, this lethargy passes off, and the replies become stronger and stronger. A good way to remove this lethargy quickly, is to give the plant a warm bath. In the heat of the midday, this state of things is reversed. That is to say, after giving vigorous replies the plant becomes fatigued, and its responses grow smaller. This fatigue passes off, however, on allowing it a period of rest. On increasing the intensity of the impinging stimulus, the response also increases. But a limit is attained, beyond which response can no longer be enhanced. Again, just as the pain of a blow persists longer with ourselves, in winter than in summer, so the same holds good of the reaction of the plant also. For instance, in summer it takes Mimosa ten to fifteen minutes to recover from a blow, whereas in winter the same thing would take over half an hour. In all this, you will recognise the similarity between human response and that of the plant.

SPONTANEOUS PULSATION

In certain tissues, a very curious phenomenon is observed. In man and other animals, there are tissues which beat, as we say, spontaneously. As long as life lasts, so long does the heart continue to pulsate. There is no effect without a cause. How then was it that these pulsations became spontaneous? To this query, no fully satisfactory answer has been forthcoming. We find, however, that similar spontaneous movements are also observable in plant tissues, and by their investigation the secret of automatism in the animal may perhaps be unravelled.

Physiologists, in order to know the heart of man, play with those of the frog and tortoise. "To know the heart," be it understood, is here meant in a purely physical, and not in a poetic sense. For this it is not always convenient to employ the whole of the frog. The heart is therefore cut out, and make the subject of experiments, as to what conditions accelerate, and what retard, the rate and amplitude of its beat. When thus isolated, the heart tends of itself to come to a standstill, but if, by means of fine tubing, it be then subjected to interval blood pressure, its beating will be resumed, and will continue uninterrupted for a long time. By the influence of warmth, the frequency of the pulsation may be increased, but its amplitude diminished. Exactly the reverse is the effect of cold. The natural rhythm and the amplitude of the pulse undergo appropriate changes, again, under the action of different drugs. Under either, the heart may come to a standstill, but on blowing this off the beat is renewed. The action of chloroform is more dangerous, any excess in the dose inducing permanent arrest. Besides these, there are poisons also which arrest the heart beat, and a very noticeable fact in this connection is, that some stop in a contracted, and others in a relaxed condition. Knowing these opposed effects, it is sometimes possible to counteract the effect of one poison by administering another.

I have thus briefly stated some of the most important phenomena in connection with spontaneous movements in animal tissues. Is it possible that in plants also any parallel phenomena might be observed? In answer to this question, I may say that I have found numerous instances of automatic movements in plants.

RHYTHMIC PULSATIONS IN DESMODIUM

The existence of such spontaneous movements can easily be demonstrated, by means of our Indian Bon charal, the telegraph plant, or Desmodium gyrans, whose small leaflets dance continually. The popular belief that they dance in response to the clapping of the hands is quite untrue. From readings of the scripts made by this plant, I am in a position to state that the automatic movements of both plants and animals are guided by laws which are identical.

Firstly, when, for convenience of experiment, we cut off the leaflet, its spontaneous movements, like those of the heart, come to a stop. But if we now subject the isolated leaflet, by means of a fine tube, to an added internal pressure of the plant's sap, its pulsations are renewed, and continue uninterrupted for a very long time. It is found again that the pulsation frequency is increased under the action warmth, and lessened under cold, increased frequency being attended by diminution of amplitude and vice versa. Under either, there is temporary arrest, revival being possible when the vapour is blown off. More fatal is the effect of chloroform. The most extraordinary parallelism, however, lies in the fact that those poisons which arrest the beat of the heart in a particular way, arrest the plant--pulsation also in a corresponding manner. I have thus been able to revive a leaflet poisoned by the application of one, with a dose of a counteracting poison.

Let us now enquire into the causes of these automatic movements so-called. In experimenting with certain types of plant tissues, I find that an external stimulus may not always evoke an immediate reply. What happens, then, to the incident energy? It is not really lost, for these particular plant tissues have the power of shortage. In this way, energy derived in various ways from without--as light, warmth, food, and so on--is constantly being accumulated, when a certain point is reached, there is an overflow, and we call this overflow spontaneous movement. Thus what we call automatic is really an overflow of what has previously been stored up. When this accumulated energy is exhausted, then there is also an end of spontaneous movements. By abstracting its stored-up heat--through the application of cold water--we can bring to a stop the automatic pulsations of Desmodium. But on allowing a first accession of heat from outside, these pulsations are gradually restored.