« ՆախորդըՇարունակել »
whole process of perfecting the seeds. It consists of seven parts, and, to illustrate them, I will sketch some particulars from the lily and other plants belonging to the same class. 1. The (calyx) cup or empalement; 2. The (corolla) blossom, petals, or flower-leaves; 3. The (stamina) stamens or chives; 4. The (pistillum) pistil or pointal; 5. The (pericarpium) seed vessel ; 6. The seed or fruit; 7. The (receptaculum) receptacle or base.
Some flowers possess all these parts, others are deficient in some of them ; but the chives, or the pointals, or both, are essential, and are to be found in all, either in the flowers on the same plant, or in different individual flowers of the same species on separate plants. I shall give you as clear a description of these several parts as I possibly can, to enable you to distinguish them at first sight. The cup, empalement, or calyx is that outer part of the flower formed of one or more green or yellowish-green leaves, sustaining the corolla at the bottom, and enclosing it entirely, before it expands, as you may remark in the rose and geranium. The empalement is either a cup, as in the polyanthus; a fence, as in the hemlock or carrot; a catkin, as in the willow or hazel; a sheath, as in the narcissus ; a husk, as in oats, wheat, or grasses ; a veil, as in mosses; or a cup, as in mushrooms.
The blossom, petals, or corolla is that beautiful coloured part of a flower which first attracts attention, and is regarded by common eyes as the flower itself; but botanists, more strict in their definitions, appropriate that term to the composition of the whole of the fructification, of which the corolla is only a part.
The stamens or chives are composed of two parts, one long and thin, by which they are fastened to the bottom of the corolla, called the filament; the other thicker, placed at the top of the filament, called anthera, or anther. Each anther is a kind of box, which opens when it is ripe, and throws out a yellow dust that has a strong smell. This is termed pollen or farina, and is the substance from which bees are supposed to make their wax.
The progress of the seed towards maturity deserves the most curious attention. First, the calyx opens, then the corolla expands and discovers the stamens, which generally form a circle within the petals surrounding the pointal. The pollen or dust which bursts from the anthers is absorbed by the pointal, and, passing through the style, reaches the germ and vivifies the seed, which, without this process, would be imperfect and barren. The stamens, pointal, and corolla, having performed their respective offices, decline and wither, making room for the seed-bud, which daily increases till it attains its perfect state.
Many curious experiments have been made by attentive naturalists that prove the necessity of this communication between the stamens and pointals of the same flower, in order to render its seeds productive. The stamens and pointal being sometimes disposed on different plants, the trial may be made by shutting up a pot of those which have pointals only in some place where they cannot be reached by the pollen of the stamens of other individual plants, and experiment has constantly shown that no seed is produced under such circumstances; but how shall we account for the conveyance of the pollen from one plant to another growing at a distance from it? They are both fixed, and cannot approach each other; yet Nature, abounding ever in resources, has provided sufficient means for the purpose. It is probable that there is an attraction between them which we may imagine but cannot perceive. This attractive quality may draw the pollen floating about in the air as it is wafted by the winds to the pointals of its own species; or, in many cases, the numerous tribes of minute winged insects which we observe so busily employed in a warm day basking and hovering upon the flowers, may soon convey this fertilising dust from one to another, and, whilst they are feasting upon
the delicious honey afforded by these flowers, return the favour by rendering them an essential service.
The pointal, or pistil, is composed of three parts : the germen, the style, and the stigma. The germen varies as to its form in different plants, but is always placed below the style: its office is to contain the embryo seeds. The style is placed on the germen and is of a variety of shapes and lengths, and sometimes seems wholly wanting. The stigma also appears of different forms, but always retains the same situaation, being invariably placed at the top of the style; or,
if that be wanting, it is fixed on the germen.
The seed-vessel, or pericarpium, is the germen of the pistil, enlarged as the seeds increase in size and approach nearer perfection. The seed vessel is divided into seven kinds :—Capsule, as in poppy and convolvulus ; pod, as in wallflower and honesty ; legume or shell, as in pea and broom; berry, as in elder and gooseberry; pome, as in apple and pear ; drupe, as in cherry and peach ; cone, as in fir and pine.
The seeds or fruit bear the same relation to the plant as the eggs of animals do to them; they are the essence of the fruit, containing the rudiments of a new plant. The formation of the seed is variously adapted to its purpose, and is composed of several parts :
1st. The heart. This is the principle of life in the future plant contained within the lobes. It consists of two parts, the plume, which ascends and forms the future stem, and the beak, which descends and becomes the roots.
2ndly. The side lobes. These supply the heart of the seed with nourishment till it is capable of extracting support from the earth. In many plants the lobes ascend in the form of leaves, and are called seed or radicle leaves ; but in some they perish beneath the surface without appearing above ground.
3rdly. The scar; an external mark where the seed was fastened within the seed vessel.
4thly. The seed coat; a proper cover to some seeds. It is of various texture and consistence in different individual plants. Sometimes the seed is crowned with the cup of the flower, and sometimes it is winged with a feather or with a thin expanded membrane, which assists the wind to waft or disperse it to a distance. The seed contains the perfect plant in embryo, though, in most instances, it is too minute to be discerned by our organs of sight; but if the seed of a bean or an acorn be sufficiently soaked in warm water, the form of the future plant may be plainly perceived.
The base or receptacle is that part by which the whole fructification is supported. In many flowers it is not very striking, but in others it is large and remarkable, as in the cotton thistle. The artichoke will also furnish us with an example. Take away the impalement, blossoms, and bristly substances, and the part remaining is the receptacle, which we eat, and call the bottom.
It remains for me to describe the nectarium, nectary, or honey-cup-an appendage with which some flowers are furnished, containing a small quantity of sweet honey-like juice, from which the bees collect their rich treasures. It is very conspicuous in some flowers—as the nasturtium, crown imperial, columbine, and larkspur—but less visible in others, and in some appears to be entirely wanting. In the dovefooted cranes-bill there are five yellowish glands which serve as a nectary. The use is supposed to be that of a reservoir, for the nourishment of the tender seed bud
A FEW BOTANICAL NOTES FOR BEGINNERS. The flowers which I have selected as examples for your examination are the crown imperial, the stock gilliflower, and
The last is chosen on account of the wonderful means used in its construction for the preservation of those
parts necessary to perfect the fruit or seed. You should watch their progress from the first appearance of the bud to the perfecting the seeds; and you can judge accurately of several of the parts only by this daily examination, as they change their form and appearance in different stages of the maturity of the flower. Gather a crown imperial as soon as you perceive one blown : if you observe it closely, you will see that it has no cup or impalement; pull off the beautifully coloured scarlet, or sometimes yellow petals, which form the corolla, one by one, and you will find that there are six of them.
The corollas of many flowers are formed of one petal, as the Canterbury bell, and are on that account called monopetalous; but those that have more petals than one in their corollas are termed polypetalous. Observe a sort of little column rising exactly in the middle of the corolla and pointing upwards. This taken in its whole is the pointal, but by a nice inspection you will find it divided into three parts—the oblong, three-cornered, swollen base, which is the germ or ovary; the style or thread placed upon this; the stigma with three notches forming its crown. Between the pointal and the corolla six other bodies will claim your notice, which you will readily guess are the stamens, composed of filaments and anthers.
Continue your visits to some other individual flower of the same kind till the petals wither and fall off, and you will perceive that the germ increases and becomes an oblong triangular capsule, within which are flat seeds in three shells. Behold the seed vessel under the form of this capsule. I had very nearly forgotten to mention the honey-cup, which may be found at the bottom of the petals in the form of a little hole. The willow wren creeps up the stems of this plant and sips the drops of honey as they hang from the petals. After having carried you through the various parts of a crown imperial, I will introduce a stock gilliflower to your notice, which I hope will afford you as much entertainment as tho