Every one skilled in natural history knows, that the mimosæ, or sensitive plants, close their leaves, and bend their joints, on the least touch. This is truly astonishing: but hitherto no end or design of nature has appeared from these motions; they soon recover themselves, and the leaves are expanded as before. Dionæ Muscipula, or Venus’s Fly Trap, is a newly discovered sensitive plant; and shows that nature may have some view towards its nourishment, in forming the upper joint of its leaf like a machine to catch food. Upon the middle of this lies the bait for the unhappy insect that becomes its prey. Many minute red glands, that cover its inner surface, and which, perhaps, discharge some sweet liquor, tempt the poor animal to taste them; and the instant these tender plants are irritated by its feet, the two lobes rise up, grasp it fast, lock the two rows of spines together, and squeeze it to death. Further, lest the strong efforts for life, in the creature thus taken, should serve to disengage it, three small erect spines are fixed near the middle of each lobe among the glands, that effectually put an end to all its struggles. Nor do the lobes ever open again, while the dead animal continues there. But it is nevertheless certain that the plant cannot distinguish between an animal and a mineral substance; for if we introduce a straw, or a pin, between the lobes, it will grasp it full as fast as if it were an insect. This plant grows in America, in wet shady places, and flowers in July and August. The largest leaves are about three inches long, and an inch and a half across the lobes: the glands of those exposed to the sun are of a beautiful red color; but those in the shade are pale, and inclining to green. The roots are squamous, sending forth few fibres, and are perennial. The leaves are numerous, inclining to bend downwards, and are placed in a circular order; they are jointed and succulent; the lower joint, which is a kind of stalk, is flat, longish, two-edged, and inclining to heart-shaped. In some varieties, they are serrated on the edges near the top. The upper joint consists of two lobes, each lobe is of a semi-oval form, with their margins furnished with stiff hairs, like eye-brows, which embrace or lock in each other when they are inwardly irritated. The upper surfaces of these lobes are covered with small red glands, each of which appears, when highly magnified, like a compressed arbutus berry. Among the glands, about the middle of each lobe, are three very small erect spines. When the lobes enclose any substance, they never open again while it continues there. If it can be shoved out, so as not to strain the lobes, they expand again; but if force is used to open them, so strong has nature formed the spring of their fibres, that one of the lobes will generally snap off, rather than yield. The stalk is about six inches high, round, smooth, and without leaves, ending in a spike of flowers. The flowers are milk-white, and stand, on foot stalks, at the bottom of which is a little painted bractea, or flower-leaf.
There is not an article in botany more admirable than a contrivance, visible in many plants, to take advantage of good weather, and to protect themselves against bad. They open and close their flowers and leaves in different circumstances; some close before sun-set, some after; some open to receive rain, some close to avoid it. The petals of many flowers expand in the sun; but contract at night, or on the approach of rain. After the seeds are fecundated, the petals no longer contract. All the trefoils may serve as a barometer to the husbandman; they always contract their leaves on an impending storm. Some plants follow the sun, others turn from it. Many plants, on the sun’s recess, vary the position of their leaves, which is styled, the sleep of plants. A singular plant was lately discovered in Bengal. Its leaves are in continual motion all day long; but when night approaches; they fall down from an erect posture to rest.[101]
A plant has a power of directing its roots for procuring food. The red whortle-berry, a low evergreen plant, grows naturally on the tops of our highest hills, among stones and gravel. This shrub was planted in an edging to a rich border, under a fruit wall. In two or three years it over-ran the adjoining deep-laid gravel walk, and seemed to fly from the border, in which not a runner appeared. An effort to come at food, in a bad situation, is extremely remarkable, in the following instance. Among the ruins of New Abbey, formerly a monastery in Galloway, there grows on the top of a wall, a plane tree, about twenty feet high. Straitened for nourishment in that barren situation, it several years ago directed roots down the side of the wall, till they reached the ground ten feet below; and now the nourishment it afforded to those roots during the time of their descending, is amply repaid, having every year, since that time, made vigorous shoots. From the top of the wall to the surface of the earth these roots have not thrown out a single fibre, but are now united in a single root.
Plants, when forced from their natural position, are endowed with the power to restore themselves. A hop-plant, twisting round a stick, directs its course from south to west, as the sun does. Untwist it, and tie it in the opposite direction, it dies. Leave it loose in the wrong direction, it recovers its natural direction in a single night. Twist the branch of a tree, so as to invert its leaves, and fix it in that position, if left in any degree loose, it untwists itself gradually, till the leaves be restored to their natural position. What better can an animal do for its welfare? A root of a tree meeting with a ditch in its progress, is laid open to the air. What follows? It alters its course, like a rational being, dips into the ground, surrounds the ditch, rises on the opposite side to its wonted distance from the surface, and then proceeds in its original direction. Lay a wet sponge near a root laid open to the air; the root will direct its course to the sponge. Change the place of the sponge; the root varies its direction. Thrust a pole into the ground at a moderate distance from a climbing plant; the plant directs its course to the pole, lays hold of it, and rises on it to its natural height. A honeysuckle proceeds in its course till it be too long for supporting its weight; and then strengthens itself by shooting into a spiral. If it meet with another plant of the same kind, they coalesce for mutual support, the one screwing to the right, the other to the left. The claspers of briony shoot into a spiral, and lay hold of whatever comes in their way for support. If, after completing a spiral of three rounds, they meet with nothing, they try again, by altering their course.
By comparing these and other instances of seeming voluntary motion in plants, with that share of life wherewith some of the inferior kind of animals are endowed, we can scarce hesitate at ascribing the superiority to the former: that is, putting sensation out of the question. Muscles, for instance, are fixed to one place as much as plants are; nor have they any power of motion, besides that of opening and shutting their shells; and in this respect, they have no superiority over the motion of the sensitive plant: nor does their action discover more sagacity, or even so much, as the roots of the plane tree, mentioned by Lord Kames.[102]
Beckmann’s History of Inventions and Discoveries presents us with an interesting account of Kitchen Vegetables and Garden Flowers, collected from numerous authorities; some parts of which I shall now transcribe, and incorporate with information derived from other sources.
Our foreign kitchen vegetables have, for the most part, been procured from the southern countries, but chiefly from Italy; and the number of them has rapidly increased, in the course of the last two centuries. Many of them require laborious attention to make them thrive in our climate. On the other hand, some grow so readily, and increase so much without culture, even in the open fields, that they have become like indigenous weeds, as is the case with hops, which at present abound in our hedges. Some plants, however, both indigenous and foreign, which were formerly raised by art and used at the table, are no longer cultivated, because we have become acquainted with others more beneficial.
Among many which were formerly cultivated, but at present are no longer esteemed, are the following. Winter-cresses, erysimum barbarea; common alexander, smyrnium olosatrum, which in the seventeenth century was used instead of celery; bulbous chærophyllum, the roots of which are still brought to market at Vienna, where they are boiled and eaten as salad. Rampion, phyteuma spicata, was formerly used in like manner. The earth nut, the tuberous roots of the lathyrus tuberosus, which grows wild in many parts of Germany, is still cultivated in Holland and in some districts on the Rhine. Rocket, brassica eruca, in Italian, ruchette, the young leaves of which were eaten by our forefathers as salad, and is still retained in Italy. And there are several others either but imperfectly known or little regarded.
Among the kitchen vegetables of which no certain traces are to be found in the works of the ancients, is spinage, spinacea oleracea. Its native country is unknown; but the name is new, and certainly derived from the nature of its prickly seeds. As far as I know, it first occurs in the year 1351, among the food used by the monks on fast-days; and at that time it was written spinagium or spinachium.
The ancients were acquainted with curled cabbages, and even with some of those kinds which we call broccoli. Under this term is understood all those species, the numerous young flower heads of which, particularly in spring and autumn, can be used like cauliflowers. The broccoli used at present was however first brought from Italy to France, together with the name, about the end of the sixteenth century.