« PreviousContinue »
means be carried over them to the fire, observing to make the current of air a little wider than that of the water below.
Crosland near Huddersfield.
The above is also the best method of preventing the dry-rot in buildings which I have ever met with, and very much exceeds in efficacy the process recommended by Dr. Parry (see Enquirer, vol. i. p. 109, et seq.) I had perfected my method, and communicated it to several friends, fifteen months before I saw Dr. Parry's.
ON VEGETABLE INSTINCT AND THE SLEEP AND SENSATION OF PLANTS.
BY MR. TUPPER.
INSTINCT is a particular disposition or tendency, in a living being, to embrace without deliberation or reflection the means of self-preservation, and to perform, on particular occasions, such other actions as are required by its economy, without having any perception for what end or purposes it acts, or any idea of the utility or advantages of its own operation.
Hence the difference between instinct and volitions; for we cannot reasonably refer to volition those particular actions for which animals have occasion, and which they spontaneously perform, even before they can have experienced those sensations upon which the .motive for action might be supposed to be founded. Of this class of actions is that of sucking; and it is very probable, that many other operations of animals which seem to be the result of volition are merely instinctive; otherwise we must, in many instances, ascribe them to a degree of intelligence and sagacity even superior to that of the human species, at least in that which relates more immediately to their necessities and welfare.
An intelligent being has for the most part some mo◄ tive in view for the performance of any particular operation; and he is thereby enabled to act in a way simi
lar to others, or differently from them, according to the object he may will or intend to accomplish. His power of action is varied almost infinitely; but with respect to irrational beings it is different. Each of these is distinguished by a certain character, which not only denotes its species, but also in a great degree marks the nature of its abilities; and therefore, in comparing the attributes of the different orders of animals, we shall find, that whatever degree of intelligence may appear to be displayed by their actions, such actions always bear some relation to the particular organization of their frame. We cannot therefore make an animal perform any work of art which is not related more or less to its natural habits; or, in other words, we cannot endue it with instincts which are foreign to its economy, unless we could at the same time new model the mechanism of its frame, and fit it accordingly for some new purposes.
The ingenuity displayed by the feathered tribe in the building of their nests, and the art and address exhibited by the spider in the weaving of its web, cannot fail to call forth the admiration of the observer. But the skill which these and many other animals exhibit, cannot be applied, even by the most sagacious of them, to purposes beyond the sphere of their particular wants. These wants are similar in every animal of the same species, and each exerts itself like the other for the purpose of providing for them, without the aid of instruction or experience. Hence, although we perceive that some particular purpose is intended by the performance of many of the actions of vegetables, as well as by those of animals, yet the intention is not in the agents themselves, but in that superintending Providence who has ordained their existence.
After these general observations, we are better prepared to consider some of those actions of vegetables which are founded upon their instinct; and a very familiar instance of motion in them, indicative of that attribute, is manifested by their universal aptitude to incline towards the light, which is so essentially necessary to their health and well being. This disposition is so great, that a plant will even twist its stem, and
change the orginal direction of its branches and leaves in order to get towards it *.
Some naturalists, however, ascribe these effects to the mechanical operation of light; but the evident benefit which a plant derives in consequence of those particular actions, as well as the circumstances attending these, render it most probable that they are the spontaneous exertion of that being to avoid what is prejudicial, and to obtain that which is more salutary to its nature; thereby, like animals, contributing to its own welfare and preservation.
If this self-inclination of a plant towards the light were the effect of the mechanical action of that element, it is reasonable to suppose that a mechanical cause, operating on a plant so powerfully as to make it change the original direction of its branches and leaves, would necessarily act with more or less force: and as, moreover, that force is continually acting during the day, we should also be led to expect that, like other mechanical stimuli frequently repeated, or long continued, it would tend to exhaust, or at least to weaken, the living powers of a plant exposed to its influence, and that more particularly at a time when from a state of debility it is less capable of resisting the exhausting effects of exciting causes. But so far from occasioning any deleterious consequences, we find that light will very essentially contribute in bringing a plant from a weak and languid condition to a state of health and vigour.
Climbing plants also afford a curious instance of instinctive economy. Some of these having very slender stems cannot, like most other plants, grow of themselves in a perpendicular direction; but, in order to compensate for this incapacity, nature has given them the power of moving or turning their branches and tendrils different ways, until they generally meet with
*It is also a remarkable and very curious fact, that even "plants in a hot-house all present the fronts of the leaves to the light; and this influences even the posture of the branches to the side where there is most light, but neither to the quarter where there is most air admitted, nor to the flue in search of heat," Vide SMITH'S "Introduction to Botany."
a tree or some other body on which to climb or attach themselves, and when a tendril has laid hold of a support, it coils up and draws the stem after it.
Trees and other vegetables have likewise the power of directing their roots for procuring nourishment; and if this does not indicate an instinctive selection of food, it is at least something very analogous to it. For instance, a tree growing near a ditch will be found to direct its roots straight downwards, on the side next the ditch, until they reach the ground below it, when they will throw off the fibres underneath, and ramify like the root on the other side of the tree. Some curious examples of this kind of instinct are related by Lord Kames, among which is the following: "A quantity of fine compost for flowers happened to be laid at the foot of a full-grown elm, where it lay neglected three or four years; when moved in order to be carried off, a network of elm fibres spread through the whole heap; and no fibres had before appeared at the surface of the ground."
Many flowers also fold up their leaves on the approach of rain, or in cloudy weather, and unfold them again when cheered by the re-animating influence of the sun. This is remarkably exemplified in the Convulvulus arvensis, Anagallis arvensis, and many others, but more particularly in the last, whence it has been called the poor man's weather-glass. In Watson's Chymical Essays, also it is stated that "trefoil, woodsorrel, mountain-ebony, the African marigold *, and many others, are so regular in folding up their leaves before rainy weather, that these motions have been considered as a kind of instinct similar to that of ants."
Aquatic plants also furnish some curious examples of spontaneous motion strongly characteristic of instinct. Among these, the water-lily affords a very remarkable instance, and that connected with the reproduction of its species. This plant bears its flowers upon a footstalk under water, and when the flowering season arrives, the stalk rises perpendicularly without any regard to the stream, until the flowers reach above the
*This refers to the petals, not leaves, of Calendulæ pluvialis.
surface of the water. At this time some of them expand, and then the antheræ discharge their fecundating dust upon the stigma. About four o'clock in the afternoon the expanded flowers close, and the foot-stalk lies down either upon or under the water. It is erected every day until the flower has been completely impregnated, when it once more sinks under water, and there remains to ripen its seeds, which, at a proper time, escape from the fruit, and give birth to new individuals.
This is asserted by Linnæus and various other naturalists; and, though controverted by some, has been recently confirmed by the observations of Dr. Smith, who authorizes me to make use of his name on this occasion. In cold or shady weather this phenomenon is less evident, and is explained by the writer last named as entirely owing to the stimulus of light. But yet, I presume, it is also in part referable to instinct, and that light operates only as an auxiliary to that pheno
Besides the above examples of spontaneous motion in vegetables, there are other instances of it which take place on such particular occasions, as strongly indicate the presence of sensation in this class of beings; and if they are endued with any degree of it, may we not very consistently suppose that they are also capable of instinctive actions? These instances of motion are observed towards evening, and during the night, when plants are supposed to have also their season of sleep ; and the external character of many of them appears so changed at the time, that it is often difficult to recognize their species. In some plants the leaves hang down by the side of the stem; in others, they rise and embrace it, and in some they are disposed in such a way as to conceal all the parts of fructification.
Motions of a similar kind also take place in the flowers. Some of these during the night fold themselves up in their calices; some only close their petals, while others incline their mouth or opening towards the ground. The mode of sleep varies, therefore, in different species of plants; and in consequence of this alteration of position in the flowers as well as the leaves, the young and tender stems, buds, fruits, &c.