THE old prophets took the "flowers of the field" as the most natural emblems of the life and immortality of man, and we repeat the words without knowing how true the comparison and how close the analogy between the life of a plant and the life of a man. Under the genial influence of spring weather, the little seed bursts the sheath in which it has been bound and preserved during the long winter months, and sends downwards into the earth a tiny fibre, and upwards into light and air a young stem, to which are attached the first pair of leaves. We see these leaves bespangling the bare loam and dotting the mould on a warm spring day suddenly and without warning; These are the nursing leaves of the young embryo. They are thick and fleshy, and are formed of the bulk of the seed. These cotyledons, as the botanists call them, perform a duty peculiar to themselves. They are full of starchy matter, which enables them to feed the young plant until the true aerial leaves appear.
These nursing leaves are not only different in texture and in form from the later leaves, but they differ in various species from one another in a less degree than the true leaves. Through these leaves the little stem bears aloft the plant of the future; and by the aid of the sugary compound called dextrine, formed by the seed-leaves and the moisture of the earth and atmosphere, the rootlets and the plant grow and flourish, until the exhausted seed-leaves wither away, and the plant assumes an independent existence. Prior to this it had a simple parasitical existence. It now changes its organism with a change of diet, and the stage of infancy is past.
From the earth and atmosphere alone the plant now derives its store of food. The rootlet sends forth its tiny white fibres in search of food. The stem ascends into the air, binding as it goes its fibres together in separate cylindrical beds by the bark or skin. At regular and definite points the leaves appear, and through their surface the fibres of the wood permeate as veins, veinlets, and capillaries, connected directly with the fibres of the stem and roots, and thus forming a direct channel of communication from one extremity of the plant to the other. Like the blood in the human veins, the sap is carried through the whole structure of the plant, to be aerated and spread out by the leaves, which act as the lungs of the plant, throwing out refuse or absorbing new matter from the atmosphere. The process of evaporation and absorption is aided by the peculiar organization of the epidermis or skin of the leaves. The porous openings in the skin are called stomata, and are really beautiful self-acting valves. If we take the leaf of a lily, where these stomata are large, and carefully remove the skin and the chlorophyll or leaf-green, and call in the aid of a microscope, we shall see that these valves consist of two oval cells, as a rule, with a slit in the middle, and these open directly into the hollow chambers or air-cavities in the interior of the leaf. By these the necessary gases are absorbed from the atmosphere, and the surplus moisture of the sap evaporated. The growth of the plant is now rapid. New leaves and new rootlets are produced in rapid succession. At first the growth of the plant is accelerated, and then retarded. The "wave of growth," if I may use the term, begins to recede about the middle of the plant. Afterwards the force and energy of the plant is devoted to a new function - that of reproduction. The leaves are crowded into rosettes, or clusters, of different forms and colours, which we call by the name of flowers. The vegetative force of the plant is now at zero - the vegetative stage of youth passed away - for ever in an annual plant, for a season in perennial plants, when the process is again renewed.
1. Ply Orchis, 2.Foxglove. 3. Salad Burnet. 4. Scabious. 5. Corn Marigold. 6. Bluebottle. 7. Bittersweet 8. Mallow.
In the meantime the plant enters on the period of puberty. The leaves crowd together - their structure changes. The flower appears, which is only the leaves in another shape; and these shapes vary. In some the various parts are well defined; in others they are all blended together, as if Nature laughed in scorn at the attempts man has made to confine her within the fetters of an artificial nomenclature, or to define her handiwork. I will, for the sake of those who have not trodden these paths before, use the convenient distinction of parts to be found in highly organized flowers. These are five in number, but one is only a continuation of the other, so that there are but four sets of metamorphosed leaves - the calyx, the corolla, the stamens, and the pistil. The receptacle is merely the base on which these four parts are situated. The true botanical flower is the pistil and stamens - the popular coloured flower the calyx and corolla.
Let us consider these parts separately. The outer-most cluster of the floral leaves, and which are generally of a green colour, is called the calyx - literally the flower-cup. It is sometimes divided into individual leaves, as the buttercup, daisy, and strawberry show. These are called sepals. In some plants, as in the tulip, the calyx is not visible, but the next set of leaves, called the corolla, is largely developed. This is the popular part of the flower, and simply means the garland. The single leaves of the corolla are called petals: thus the red petals of the rose, and the yellow petals of the buttercup, constitute the corolla of these plants.
The stamens are slender thread-like filaments situated immediately within the corolla. They are very conspicuous in the lily, which has six. In the stamen we see the stalk of the leaf converted into a filament, and the delicate portion or blade into a club-like ball or head, which is called ananther. This anther contains two small lobes or cells, which contain a fine dust, called pollen. This is the fertilizing matter of the flower.
Calyx of Celandine.
Corolla of Tulip.
The pistil is the central pillar, very conspicuous in the lily and tulip, but is absent in some flowers. It consists of a leaf folded on its mid-rib, the two sides of the lamina or blade of which are united at their margins, to form the ovary. The summit of this folded leaf, denuded of its epidermis, corresponds to the stigma or head of the pistil. The part of the pistil between the stigma and ovary is called the style. The pistil, when present, is always in the centre of the flower, and the stamens surround it. The ovary is so named because it contains the ovules, which, after fertilization, are converted into seed.
The process of fertilization takes place when all the flowers are fully expanded and matured. The anthers at first are moist and closed; but as they approach maturity, they become dry, their cells are ruptured, and they discharge their dust-like pollen on the stig-matic surface of the pistil, which is provided with a clammy juice, to retain the pollen-grains. These grains absorb the exuded fluid, swell out, and finally emit delicate tubes, which penetrate the style, and con-vey the fertilizing fluid to the ovules in the germcn or ovary. Then the miniature plant begins to be formed, and the ovules are gradually transformed into seed. The flowers fade, the leaves wither, and the plant dies; but as it does so it becomes an object of still deeper admiration. Each part which has fulfilled its mission disappears. The new vitality which is established in the ovary absorbs all the vegetative power of the plant. The radish, garden pea, and numerous other well-known plants show this process. The seed-pod is but the enlarged ovary which starts out of the calyx, and as the seed ripens the plant dies. If we take up the seed and open it, we shall see the seed-leaves or cotyledons, the eye or helium, and the embryo or heart. If you take a bean, and leave it in a damp place until it begins to sprout, you will be able to see how beautifully each part fulfils its mission, and prepares to enter on its life's career.
Stamen of Lily.
To enable it to do this under the most favourable circumstances, the seed-vessel is so organized that the seeds may be dispersed. The dandelion and the thistle cast their downy seeds to the wind; the furze bush and the balsam open their seed-vessels with a spring, and project their seeds to a considerable distance; others have their seeds contained in a luscious fruit; others cling - as the burdock and teazle - to every passing thing. Ultimately they find a home, and spring up in all their marvellous beauty, "woven by the magic chemistry of Nature from earth and air, and coloured by the distant sun."
There are other phases of plant life which can only be indicated rather than defined here. Day by day the plants arise out of a seeming sleep. In the day-time they breathe out oxygen and absorb carbonic acid: thus they fulfil an important function in the laboratory of Nature. At night they give out carbonic acid, but to such a small extent as to render the injurious consequences likely to arise therefrom very small indeed. If we lived in perpetual night, the earth would cease to be habitable; without daylight the plants could not form the chlorophyll or leaf-green. The flowers are coloured by the sun. When the petals are folded together in the bud, they are of a greenish hue, and they only acquire their radiance and beauty by a direct exposure to the sun's rays.
Some flowers go through periodic changes of colour; others change their perfume with the changing hours; others their taste. Many plants are weather prophets: some keep their faces to the sun; others close at periodic times. The goat's-beard, for instance, closes at noonday, and has received the popular cognomen of "Jack Go-to-bed;" and it is very doubtful if its first name is not a corruption of the latter. Linnaeus was enabled to construct what he called a "horologium flora" or floral clock, by strict attention to these habits of the flowers. Thus the common morning glory opens at dawn, the star of Bethlehem a little after ten o'clock, the ice plant at twelve o'clock at noon, at which time the goat's-beard and morning glory close, unless, indeed, the day is cloudy, when the latter remains open the whole day. The four-o'clock opens about that time in the afternoon; the flowers of the thorn-apple and the evening primrose open at sunset; and those of the night-flowering cereus when it is dark. The white water-lily closes its flowers at sunset, and sinks beneath the water for the night. In the morning it is buoyed up by the expansion of its petals, and again floats like a Naiad on the surface as before. The slumbering and awakening of plants is not a poetic fiction: it is a reality. Here we cannot unfold what is known of the cause of this; but when plant life is more profoundly studied, then we may venture to say that human life will be better understood.
"In all places, then, and in all seasons,flowers expand their light and soul-like wings. Teaching us by most persuasive reasons How akin they are to human things."