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GENERAL OBSERVATIONS ON VEGETABLES.
"Strange there should be found Who, self-imprison'd
in their proud saloons, Renounce the odours of the open field For the unscented
fictions of the loom; Who, satisfied with only pencilled scenes, Prefer to the
performance of a God, Th' inferior wonders of an artist's hand! Lovely, indeed,
the mimic works of art, But Nature's works far lovelier."--COWPER.
1069. "THE ANIMAL AND VEGETABLE KINGDOMS," says Hogg, in his Natural History of the Vegetable Kingdom, "may be aptly compared to the primary colours of the prismatic spectrum, which are so gradually and intimately blended, that we fail to discover where the one terminates and where the other begins. If we had to deal with yellow and blue only, the eye would easily distinguish the one from the other; but when the two are blended, and form green, we cannot tell where the blue ends and the yellow begins. And so it is in the animal and vegetable kingdoms. If our powers of observation were limited to the highest orders of animals and plants, if there were only mammals, birds, reptiles, fishes, and insects in the one, and trees, shrubs, and herbs in the other, we should then be able with facility to define the bounds of the two kingdoms; but as we descend the scale of each, and arrive at the lowest forms of animals and plants, we there meet with bodies of the simplest structure, sometimes a mere cell, whose organization, modes of development and reproduction, are so anomalous, and partake so much of the character of both, that we cannot distinguish whether they are plants or whether they are animals."
1070. WHILST IT IS DIFFICULT TO DETERMINE where the animal begins and the vegetable ends, it is as difficult to account for many of the singularities by which numbers of plants are characterized. This, however, can hardly be regarded as a matter of surprise, when we recollect that, so far as it is at present known, the vegetable kingdom is composed of upwards of 92,000 species of plants. Of this amazing number the lichens and the mosses are of the simplest and hardiest kinds. These, indeed, may be considered as the very creators of the soil: they thrive in the coldest and most sterile regions, many of them commencing the operations of nature in the growth of vegetables on the barest rocks, and receiving no other nourishment than such as may be supplied to them by the simple elements of air and rain. When they have exhausted their period in such situations as have been assigned them, they pass into a state of decay, and become changed into a very fine mould, which, in the active spontaneity of nature, immediately begins to produce other species, which in their turn become food for various mosses, and also rot. This process of growth and decay, being, from time to time, continued, by-and-by forms a soil sufficient for the maintenance of larger plants, which also die and decay, and so increase the soil, until it becomes deep enough to sustain an oak, or even the weight of a tropical forest. To create soil amongst rocks, however, must not be considered as the only end of the lichen; different kinds of it minister to the elegant arts, in the form of beautiful dyes; thus the lichen rocella is used to communicate to silk and wool, various shades of purple and crimson, which greatly enhance the value of these materials. This species is chiefly imported from the Canary Islands, and, when scarce, as an article of commerce has brought as much as £1000 per ton.
1071. IN THE VICINITY OF LICHENS, THE MUSCI, OR MOSSES, are generally to be found. Indeed, wherever vegetation can be sustained, there they are, affording protection to the roots and seeds of more delicate vegetables, and, by their spongy texture, retaining a moisture which preserves other plants from the withering drought of summer. But even in winter we find them enlivening, by their verdure, the cold bosom of Nature. We see them abounding in our pastures and our woods, attaching themselves to the living, and still more abundantly to the dead, trunks and branches of trees. In marshy places they also abound, and become the medium of their conversion into fruitful fields. This is exemplified by the manner in which peat-mosses are formed: on the surface of these we find them in a state of great life and vigour; immediately below we discover them, more or less, in a state of decomposition; and, still deeper, we find their stems and branches consolidated into a light brown peat. Thus are extensive tracts formed, ultimately to be brought into a state of cultivation, and rendered subservient to the wants of man.
1072. WHEN NATURE HAS FOUND A SOIL, her next care is to perfect the growth of her seeds, and then to disperse them. Whilst the seed remains confined in its capsule, it cannot answer its purpose; hence, when it is sufficiently ripe, the pericardium opens, and lets it out. What must strike every observer with surprise is, how nuts and shells, which we can hardly crack with our teeth, or even with a hammer, will divide of themselves, and make way for the little tender sprout which proceeds from the kernel. There are instances, it is said, such as in the Touch-me-not (impatiens), and the Cuckoo-flower (cardamine), in which the seed-vessels, by an elastic jerk at the moment of their explosion, cast the seeds to a distance. We are all aware, however, that many seeds--those of the most composite flowers, as of the thistle and dandelion--are endowed with, what have not been inappropriately called, wings. These consist of a beautiful silk-looking down, by which they are enabled to float in the air, and to be transported, sometimes, to considerable distances from the parent plant that produced them. The swelling of this downy tuft within the seed-vessel is the means by which the seed is enabled to overcome the resistance of its coats, and to force for itself a passage by which it escapes from its little prison-house.
1073. BIRDS, AS WELL AS QUADRUPEDS, are likewise the means of dispersing the seeds of plants, and placing them in situations where they ultimately grow. Amongst the latter is the squirrel, which is an extensive planter of oaks; nay, it may be regarded as having, in some measure, been one of the creators of the British navy. We have read of a gentleman who was walking one day in some woods belonging to the Duke of Beaufort, near Troy House, in Monmouthshire, when his attention was arrested by a squirrel, sitting very composedly upon the ground. He stopped to observe its motions, when, in a short time, the little animal suddenly quitted its position, and darted to the top of the tree beneath which it had been sitting. In an instant it returned with an acorn in its mouth, and with its paws began to burrow in the earth. After digging a small hole, it therein deposited an acorn, which it hastily covered, and then darted up the tree again. In a moment it was down with another, which it buried in the same manner; and so continued its labour, gathering and burying, as long as the gentleman had patience to watch it. This industry in the squirrel is an instinct which directs it to lay up a store of provision for the winter; and as it is probable that its memory is not sufficiently retentive to enable it to recollect all the spots in which it deposits its acorns, it no doubt makes some slips in the course of the season, and loses some of them. These few spring up, and are, in time, destined to supply the place of the parent tree. Thus may the sons of Britain, in some degree, consider themselves to be indebted to the industry and defective memory of this little animal for the production of some of those "wooden walls" which have, for centuries, been the national pride, and which have so long "braved the battle and the breeze" on the broad bosom of the great deep, in every quarter of the civilized globe. As with the squirrel, so with jays and pies, which plant among the grass and moss, horse-beans, and probably forget where they have secreted them. Mr. White, the naturalist, says, that both horse-beans and peas sprang up in his field-walks in the autumn; and he attributes the sowing of them to birds. Bees, he also observes, are much the best setters of cucumbers. If they do not happen to take kindly to the frames, the best way is to tempt them by a little honey put on the male and female bloom. When they are once induced to haunt the frames, they set all the fruit, and will hover with impatience round the lights in a morning till the glasses are opened.
1074. Some of the acorns planted by the squirrel of Monmouthshire may be now in a fair way to become, at the end of some centuries, venerable trees; for not the least remarkable quality of oaks is the strong principle of life with which they are endued. In Major Rooke's "Sketch of the forest of Sherwood" we find it stated that, on some timber cut down in Berkland and Bilhaugh, letters were found stamped in the bodies of the trees, denoting the king's reign in which they were marked. The bark appears to have been cut off, and then the letters to have been cut in, and the next year's wood to have grown over them without adhering to where the bark had been cut out. The ciphers were found to be of James I., William and Mary, and one of King John. One of the ciphers of James was about one foot within the tree, and one foot from the centre. It was cut down in 1786. The tree must have been two feet in diameter, or two yards in circumference, when the mark was cut. A tree of this size is generally estimated at 120 years' growth; which number being subtracted from the middle year of the reign of James, would carry the year back to 1492, which would be about the period of its being planted. The tree with the cipher of William and Mary displayed its mark about nine inches within the tree, and three feet three inches from the centre. This tree was felled in 1786. The cipher of John was eighteen inches within the tree, and rather more than a foot from the centre. The middle year of the reign of that monarch was 1207. By subtracting from this 120, the number of years requisite for a tree's growth to arrive at the diameter of two feet, the date of its being planted would seem to have been 1085, or about twenty years after the Conquest.
1075. Considering the great endurance of these trees, we are necessarily led to inquire into the means by which they are enabled to arrive at such strength and maturity; and whether it may be considered as a humiliation we will not determine, but, with all the ingenious mechanical contrivances of man, we are still unable to define the limits of the animal and vegetable kingdoms. "Plants have been described by naturalists, who would determine the limits of the two kingdoms, as organized living bodies, without volition or locomotion, destitute of a mouth or intestinal cavity, which, when detached from their place of growth, die, and, in decay, ferment, but do not putrefy, and which, on being subjected to analysis, furnish an excess of carbon and no nitrogen. The powers of chemistry, and of the microscope, however, instead of confirming these views, tend more and more to show that a still closer affinity exists between plants and animals; for it is now ascertained that nitrogen, which was believed to be present only in animals, enters largely into the composition of plants also. When the microscope is brought to aid our powers of observation, we find that there are organized bodies belonging to the vegetable kingdom which possess very evident powers of locomotion, and which change about in so very remarkable a manner, that no other cause than that of volition can be assigned to it." Thus it would seem that, in this particular at least, some vegetables bear a very close resemblance to animal life; and when we consider the manner in which they are supplied with nourishment, and perform the functions of their existence, the resemblance would seem still closer. If, for example, we take a thin transverse slice of the stem of any plant, or a slice cut across its stem, and immerse it in a little pure water, and place it under a microscope, we will find that it consists principally of cells, more or less regular, and resembling those of a honeycomb or a network of cobweb. The size of these varies in different plants, as it does in different parts of the same plant, and they are sometimes so minute as to require a million to cover a square inch of surface. This singular structure, besides containing water and air, is the repository or storehouse of various secretions. Through it, the sap, when produced, is diffused sideways through the plant, and by it numerous changes are effected in the juices which fill its cells. The forms of the cells are various; they are also subject to various transformations. Sometimes a number of cylindrical cells are laid end to end, and, by the absorption of the transverse partitions, form a continuous tube, as in the sap-vessels of plants, or in muscular and nervous fibre; and when cells are thus woven together, they are called cellular tissue, which, in the human body, forms a fine net-like membrane, enveloping or connecting most of its structures. In pulpy fruits, the cells may be easily separated one from the other; and within the cells are smaller cells, commonly known as pulp. Among the cell-contents of some plants are beautiful crystals, called raphides. The term is derived from [Greek: rhaphis] a needle, on account of the resemblance of the crystal to a needle. They are composed of the phosphate and oxalate of lime; but there is great difference of opinion as to their use in the economy of the plant, and one of the French philosophers endeavoured to prove that crystals are the possible transition of the inorganic to organic matter. The differences, however, between the highest form of crystal and the lowest form of organic life known, viz., a simple reproductive cell, are so manifold and striking, that the attempt to make crystals the bridge over which inorganic matter passes into organic, is almost totally regarded as futile. In a layer of an onion, a fig, a section of garden rhubarb, in some species of aloe, in the bark of many trees, and in portions of the cuticle of the medicinal squill, bundles of these needle-shaped crystals are to be found. Some of them are as large as 1-40th of an inch, others are as small as the 1-1000th. They are found in all parts of the plant,--in the stem, bark, leaves, stipules, petals, fruit, roots, and even in the pollen, with some few exceptions, and they are always situated in the interior of cells. Some plants, as many of the cactus tribe, are made up almost entirely of these needle-crystals; in some instances, every cell of the cuticle contains a stellate mass of crystals; in others, the whole interior is full of them, rendering the plant so exceedingly brittle, that the least touch will occasion a fracture; so much so, that some specimens of Cactus senilis, said to be a thousand years old, which were sent a few years since to Kew, from South America, were obliged to be packed in cotton, with all the care of the most delicate jewellery, to preserve them during transport.
1076. Besides the cellular tissue, there is what is called a vascular system, which consists of another set of small vessels. If, for example, we, early in the spring, cut a branch transversely, we will perceive the sap oozing out from numerous points over the whole of the divided surface, except on that part occupied by the pith and the bark; and if a twig, on which the leaves are already unfolded, be cut from the tree, and placed with its cut end in a watery solution of Brazil-wood, the colouring matter will be found to ascend into the leaves and to the top of the twig. In both these cases, a close examination with a powerful microscope, will discover the sap perspiring from the divided portion of the stem, and the colouring matter rising through real tubes to the top of the twig: these are the sap or conducting vessels of the plant. If, however, we examine a transverse section of the vine, or of any other tree, at a later period of the season, we find that the wood is apparently dry, whilst the bark, particularly that part next the wood, is swelled with fluid. This is contained in vessels of a different kind from those in which the sap rises. They are found in the bark only in trees, and may be called returning vessels, from their carrying the sap downwards after its preparation in the leaf. It is believed that the passage of the sap in plants is conducted in a manner precisely similar to that of the blood in man, from the regular contraction and expansion of the vessels; but, on account of their extreme minuteness, it is almost an impossibility to be certain upon this point. Numerous observations made with the microscope show that their diameter seldom exceeds a 290th part of a line, or a 3,000th part of an inch. Leuwenhoeck reckoned 20,000 vessels in a morsel of oak about one nineteenth of an inch square.
1077. In the vascular system of a plant, we at once see the great analogy which it bears to the veins and arteries in the human system; but neither it, nor the cellular tissue combined, is all that is required to perfect the production of a vegetable. There is, besides, a tracheal system, which is composed of very minute elastic spiral tubes, designed for the purpose of conveying air both to and from the plant. There are also fibres, which consist of collections of these cells and vessels closely united together. These form the root and the stem. If we attempt to cut them transversely, we meet with difficulty, because we have to force our way across the tubes, and break them; but if we slit the wood lengthwise, the vessels are separated without breaking. The layers of wood, which appear in the stem or branch of a tree cut transversely, consist of different zones of fibres, each the produce of one year's growth, and separated by a coat of cellular tissue, without which they could not be well distinguished. Besides all these, there is the cuticle, which extends over every part of the plant, and covers the bark with three distinct coats. The liber, or inner bark, is said to be formed of hollow tubes, which convey the sap downwards to increase the solid diameter of the tree.
1078. THE ROOT AND THE STEM NOW DEMAND A SLIGHT NOTICE. The former is designed, not only to support the plant by fixing it in the soil, but also to fulfil the functions of a channel for the conveyance of nourishment: it is therefore furnished with pores, or spongioles, as they are called, from their resemblance to a sponge, to suck up whatever comes within its reach. It is found in a variety of forms, and hence its adaptation to a great diversity of soils and circumstances. We have heard of a willow-tree being dug up and its head planted where its roots were, and these suffered to spread out in the air like naked branches. In course of time, the roots became branches, and the branches roots, or rather, roots rose from the branches beneath the ground, and branches shot from the roots above. Some roots last one year, others two, and others, like the shrubs and trees which they produce, have an indefinite period of existence; but they all consist of a collection of fibres, composed of vascular and cellular tissue, without tracheae, or breathing-vessels. The stem is the grand distributor of the nourishment taken up by the roots, to the several parts of the plant. The seat of its vitality is said to be in the point or spot called the neck, which separates the stem from the root. If the root of a young plant be cut off, it will shoot out afresh; if even the stem be taken away, it will be renewed; but if this part be injured, the plant will assuredly die.
1079. IN ACCORDANCE WITH THE PLAN OF THIS WORK, special notices of culinary vegetables will accompany the various recipes in which they are spoken of; but here we cannot resist the opportunity of declaring it as our conviction, that he or she who introduces a useful or an ornamental plant into our island, ought justly to be considered, to a large extent, a benefactor to the country. No one can calculate the benefits which may spring from this very vegetable, after its qualities have become thoroughly known. If viewed in no other light, it is pleasing to consider it as bestowing upon us a share of the blessings of other climates, and enabling us to participate in the luxury which a more genial sun has produced.