Many seeds cover themselves for protection with a hard shell, and in order to be devoured and carried farther by animals, which in their excrements directly supply them with manure, they envelop themselves in savoury pulp (stone-fruit, grapes, gooseberries, currants, &c.), or they peripherally surround a carnose nucleus (strawberries, &c.) The seeds of aquatic plants are usually heavier than water, and accordingly sink to the bottom. Those of most lofty trees, on the contrary, are light, and are transported on the surface of the water far and wide to new stations by wind and current. The mango-tree (Rhizophora mangle) grows, at the mouths of rivers and on flat sea-shores, in the mud, so far as the same is covered over by the salt flood, thrives therefore only on a narrow strip, wherefore the seeds must take firm root beside the mother tree. On the receptacle of the flower of this tree now there is gradually produced a pulpy hollow growth, by which the seed, with the help of a stalk inch long, is pushed out, so that after about a year it depends perpendicularly. The seed itself is 10 inches long, thicker and heavier towards the free end, but terminating with a puncheonshaped point. It sprouts within its covering, and even develops an important root. Through its form and weight the falling seed penetrates water and mud three to four feet, and penetrates the ground yet one inch more, where it can then soon fasten itself with its root.—These examples may suffice to show, that even the vegetable soul performs sufficiently wonderful works in setting up appropriate mechanisms, whose end is even in part tolerably remote.
(b.) The Recuperative Power of Nature.—Animals have each organ only just as often as the whole organism requires it for its maintenance; hence the endeavour to replace a lost one in the same way. The Idea of the plant demands a numerically unlimited repetition of the same organs; wherefore also a partial loss usually is not prejudicial to the persistence of the whole. Here, then, no reason exists for restoring the lost parts at the same place and in the same manner, since the plant finds it much easier to accomplish the replacement at other places by means of the already existing buds. Nevertheless, sufficient opportunities are afforded for seeing that in the plant likewise the vis medicatrix is active, it is only necessary to deprive a plant of a certain class of organs which is essential for its existence, e.g., all the roots, when it will immediately put forth new roots, or die when it has no longer the requisite force. Also the process of cicatrising wounds or cut surfaces is altogether analogous to that of animals.
Finally, in the plant as in the animal, the whole life is an infinite sum of infinitely numerous acts of the vis medicatrix, since at each moment the destructive physical and chemical influences must be paralysed and met.
(c.) Reflex Movements.—The physiologists distinguish reflex movement and “simple stimulation of contractile tissue.” This is correct when one inquires where the reflexion of the stimulus into motion takes place; namely, whether the seat of reaction lies at the stimulated spot itself or at another; it is, however, a mistake to try to find herein a difference of principle. The essence of reflexion in both cases is conversion of an active stimulus into reactive motion; an absolute restriction to the irritated point is at the same time never met with; but whether the conduction proceeds a little further or not can make no difference in principle. That which stamps a reactive movement as reflex action is the inadequacy of merely material natural laws for its production; only when we can rest content with these (e.g., elasticity, chemical reaction), only then can we deny reflex action, whose essence is an unconscious psychical, an instinctive reaction. Whether a reflexion is effected by nerves and muscles, or by other equivalent mechanism, can by no means justify a difference in principle, since the strictly active matter is still always the protoplasm, whether free or enclosed in various kinds of cells.
If the water inhabited by a polype be shaken, the polype contracts into a bundle. This will be called by every one reflex action, no matter whether in future, in the homogeneous slimy mass of the polype, the analogues of nerves and muscles be discovered or not. And when the Mimosa pudica, shaken by the tread of the passer-by, shrinks along with its leaves, is this not reflex action? When the irritated penis is erected in virtue of change of blood-circulation, this is admitted to be reflex movement, and in the case of the plant is not the altered sap-circulation to be considered just as good a means to reflex movement? For the plant indeed does not need the continuous quick movements for which the animal requires its muscles, accordingly muscles would be a useless luxury for it. In the animal the sign of reflexion is that about the same reaction occurs, whether one applies a mechanical, chemical, thermal, galvanic, or electric stimulus; the same is, however, also the case with plants, whereas dead mechanisms are wont to respond only to a quite definite stimulus. Strong electric shocks annihilate animal as well as vegetable irritability. If a needle, connected with the positive pole of a galvanic battery, be stuck through the stalk of a barberry flower, and the wire of the negative pole be united with a petal by means of a lightly affixed moist piece of paper, at the moment of closing the chain the stamen belonging to the leaf springs over to the pistil. If the pole be changed, the current is less active, just as animal preparations more powerfully react when the negative pole is united with the peripheral end. On opening the chain no movement takes place, just as with frog’s thighs. According to Blondeau the constant current, with application of the necessary precautions, acts on the Mimosa pudica just as little as on animal muscles as a motor stimulus, whilst the intermittent induction current proves to be a very violent stimulus. The part of an irritated animal slowly returns to its position on the abolition of the stimulus; thus, e.g., an irritated oyster or polype quickly shrinks, but opens slowly. A repetition of the stimulation blunts the irritability, rest restores it. Further, the irritability manifests itself differently according to condition of health, age, sex, season, state of the weather, and other circumstances. All this occurs with plants precisely as with animals.
The reflex movements of the Dioncæa muscipula I have already mentioned above. If an insect deposits itself on a leaf of the same, it is first of all retained there, being caught by the hairs, and then gradually the whole leaf coils round it. Here we have upon a simple stimulus at a single spot a partly simultaneous, partly appropriate successive participation of many places of the leaf, precisely as we are accustomed to find in animals, only that instead of the monarchical command of a nerve centre, a republican participation of all the parts in harmonious agreement has place. The phenomenon is more centralised, and therefore more animal-like in all leaves, anthers, &c., where the seat of reaction is to be sought in the joints, by which these parts are fastened.
In many flowers the ripe anthers gradually spontaneously incline towards the pistil, in some a joint is formed, which, on the stimulus of some insect, jerks the pollen on to the stigma. In others the crooked stigma is also irritable, and extends on a stimulus affecting it, whereby it carries off pollen from the anthers. Mimosa pudica has bipinnate leaves, and the leaflets, nerves, the chief leaf-stalk, nay, even the branch, have each their special movement. If cautiously avoiding all shaking, some strong acid be applied to a leaflet by degrees, all the adjacent leaves close up; according to Dutrochet, the velocity of propagation amounts from eight to fifteen millimetres in a second in the leaf-stalks, in the stigma, at the most, from two to three millimetres. Here the conductivity is actually visible. The same result is reached when a leaflet is gently scorched; the leaves fold up much beyond that required by the effect of the heat. Brücke, and subsequently Bert, proved that in this remarkable plant the spontaneous movements, which consist in a raising and lowering of the petioles according to the time of day, are to be well distinguished from the movements resulting from stimulation, since the capacity of the plant for the latter is paralysed by ether vapours, which, indeed, act likewise narcotically on the nervous system of the animal, whereas the former are propagated unchanged. That the diurnal elevations and depressions depend on regular alternations of the sap-circulation is undoubted; by what means the tens
ion of the upper and lower knots on the petioles is changed on occasion of a stimulus has indeed not been directly established for Mimosa pudica, but certainly for the above-mentioned pollen of Berberis vulgaris. Here, namely (as in most vegetable parts), an opposite tension on the part of various tissues takes place, in that the exterior coating strives to shorten the filament, the underlying protoplasm endeavours to lengthen it. If, now, a suitable stimulus approaches the inner side of the filament, the protoplasm contracts; and while, in this way, the previous equilibrium of the tensions is changed in favour of the exterior coating, this can realise its tendency to shortening, and by this means bends the filament. The action, which liberates the play of existing forces, is thus here a contraction of the protoplasm, precisely as in lower animals or as in muscles of higher ones.
It is impossible to mistake the thorough-going analogy between the reflex actions of animals and plants; the differences reach only just as far as the general arrangement of the organisms and as the special ends of each reaction differ. If, now, the reflex actions in animals have once for all been recognised as in the last resort acts of a psychical nature, one cannot avoid claiming this unconscious psychical element also for plants, just as one must reckon it to every animal part, which is still per se capable of reflex movements.
(d) Instinct.—We saw already in the animal kingdom the inseparability of instinct, reflex movement, and organic formation; in the vegetable kingdom they can still less be separated, for, on the one hand, on account of the defective means of movement for the plant, organic formation must accomplish much by appropriate mechanisms which the animals perform with instinctive movement (think of coition and the dissemination of the seeds), and on the other side the consciousness of plants stand so low, that the difference between the stimulus of reflex movement and the motive of instinctive action must shrink to a minimum. Nevertheless we shall still find abundant traces, which unmistakably confront us as the same as that which we call instinct in the animal kingdom. A polype instinctively betakes itself from the shaded half of its vessel to that illuminated by the sun, and when Oscillatoriæ do the same, when the sunflower almost dislocates its neck in order to turn its face to the sun, is that not to be called instinct? Dutrochet relates in his Rech. p. 131: “I saw the leaf of a plant standing in the open air, whose upper surface was covered with a small board, try to withdraw itself from the screen by means which were not always the same, but were always of a kind which must most easily and quickly lead to the goal; thus this happened now by means of a lateral bending of the leaf-stalk, now by a bending of the same leafstalk towards the pedicle.”
Knight saw a vine-leaf, whose under side was illuminated by the sun, and whose approach to a natural position he had blocked in every way, make almost every possible attempt to turn to the light the right side, with which it was mainly necessitated to respire. After it had for a few days attempted to approach the light in a certain direction, and by bending back its lobes had almost covered its whole under-side therewith, it spread itself out and removed further from the window of the glass-house, in order to approach the light in the opposite direction (Treviranus, Beiträge, 119). Frank (Die natürl. wagerechte Richtung, &c., Leipzig, 1870) has recently confirmed this, and extended it to a number of other plants. According to him also it is noticeable that this movement is always executed by the shortest course, the leaf turning now up, now down, now right, now left. The wonder is not diminished by the circumstance that the leaves, or leaf-stalks, lose this capability when their growth is complete, except when they are provided with special cushion-like swellings at the base of the stem, which on every occasion may again receive changes of dimension, which during the period of growth are to be looked upon as relatively violent modifications of the same.—Dutrochet covered the terminal leaf of a three-leaved bean-leaf (Phaseolus vulgaris) with a small board. As the shortness of the special leaf-stalk made retreat impossible to the leaflet, this took place by the bending of the joint petiole, whereas in the dark the board was not evaded. “If,” says the investigator, “one sees how many means are here applied to attain the same end, one will be almost tempted to believe there dwells here a secret intelligence which chooses the most appropriate means for the attainment of the end.” So, driven by the simple power of facts, does a naturalist utter a truth, which is only incomprehensible to him, because he is not acquainted with unconscious psychical activity. That there is here no mere reflex action on a stimulus is easy to see, for it is just the want of a necessary stimulus which is evaded.
Tolerably familiar are the phenomena of vegetable sleep, whereby the leaves are partly lowered, partly inverted, the flowers lower their heads or shut up. In fact, these phenomena have been already mentioned and find their end in protecting the pollen grains from the dew. That the depression of the petals, however, does not depend on mere exhaustion, we may easily convince ourselves; in their bent condition they are rather in a state of tension and elastic. Malva peruviana, by rearing the leaves round the stalk at the tip of the branches forms in the dormant condition a kind of funnel, under which the young flowers or leaves are protected; Impatiens-noli-metangere forms out of the depressed upper leaves an arch for the young sprouts, some others enclose the flowers by folding the leaflets of their compound leaves. The time for sleep and waking are as different for plants as for animals. Many of our plants bend towards the sun, others punctually keep fixed times, no matter into what climate they are transferred, no matter whether it be summer or winter. One sees from this that these periodical movements also are partially independent of external stimuli and arise purely from internal conditions of the plant itself; they are simply instinctively regulated efforts.
In many plants the stamina incline towards the pistil for purposes of fertilisation, shed their pollen, and then return to their position; in others the pistil moves towards the stamens; in yet others, both mutually seek each other (Treviranus, Physiologie der Gewächse, ii. 389). In Lilium superbum, Amaryllis formosissima, and Pancratium maritimum, the anthers successively approach the stigma. In Fritillaria persica, they alternately bend towards the style. In Rhus coriaria, two or three filaments simultaneously protrude, describe a quadrant, and bring their anthers quite close to the stigma. In Saxifraga tridactilytes, muscoides, aizoon, granulata, and cotyledon, two stamens approach each other from opposite sides above the stigma, and again spread, after they have scattered their pollen, in order to make room for others. In Parnassia palustris the male parts move to the female in the same order in which the pollen matures, and indeed, when they approach the stigma, quickly and at once, when they again separate after fertilisation, in three periods. In Tropæolum they elevate themselves one after the other from the originally depressed filaments at the period of full bloom, and after the anthers have shed their pollen on the stigma bend down again, in order to make room for others. One cannot wish for a clearer indication of instinct than is presented in these examples; for here the motive is the presence of the stigma, and the maturity of the pollen, but the order in which, and the fashion in which the stamens move to and fro wears just as much the semblance of caprice as any animal movement can.
Remarkable are the instinctive movements of climbing plants (vide Mohl, On the Winding of Tendrils). Such a plant first grows somewhat perpendicularly upwards, then its stalk bends horizontally, and describes circles, in order to seek a support in the environment, just as an eyeless caterpillar describes circles with its anterior parts to seek a new leaf. The longer the pistil grows the larger, of course, become the circles; that is, if the plant finds no support in the environment it seeks it in a wider circuit. Finally, if the stalk can no longer support its own weight it falls to the ground, and now creeps further in a straight direction. If it now finds a support it might either take no notice of it, or, for convenience sake, run indeed further along the earth in order not to be obliged to climb; in point of fact, however, it immediately grasps its support and climbs up by it spirally. Yet here, too, the plant still proc
eeds by way of selection; the flat side (especially in the young stalk) does not wind itself about dead organic or inorganic supports, but only about living plants, by which it eagerly climbs upwards, for the roots cleaving to the earth soon die, and it is then entirely assigned to the food, which it imbibes with its papillae from the clasped plant. Every creeping plant by nature either moves to the right or to the left, If one unrolls a young convolvolus from its support and winds it round again in the opposite direction, it will return into its original spiral direction, or will surrender its life in the endeavour. This too answers to the animal instincts. If however, one allows two such plants mutually to embrace without foreign support, and so to climb by one another’s aid, the one voluntarily changes its solitary direction in order to make this mutual embrace possible (Farmer’s Magazine, repeated in the Times of the 13th July 1848). Thus, instead of adapting itself to the powerful change, the plant prefers to sacrifice its life; but when this change is judicious, it anticipates it of its own accord. Here one finds even the variability of animal instinct in the most remarkable form.
(e) The Instinct for Beauty in plants cannot in this place be further proved. I hold the assertion to be correct also for the vegetable kingdom, that every being builds itself up as beautifully as is compatible with the ends of its existence, and so far as it can subdue the stubborn material. Whether one considers the greatest or the least in the vegetable kingdom, the stately oak or the microscopic moss; whether one looks to the whole or the individual, to the glorious primæval forest or the fir cone, everywhere that truth will be found confirmed.
Philosophy of the Unconscious Page 54
