anther. (Fig. 4 b.) The ripe dust or pollen from the anther, carried upon the stigma, fertilizes the ovules.

N.B.—The first ten classes of the Linnæan system of classification are distinguished by the number of stamens, the other fourteen classes principally by their arrangement.

(d.) The pistil and stamen are the only essential parts of a flower. The beautiful floral leaves usually surrounding them are not essential, and in many cases are altogether wanting. If the stamens and pistils are in different flowers upon the same plant, the flowers are called monacious, i.e., in one house, though separated. If they are in different flowers upon different plants they are called diæcious, i.e., in two houses. If they are either separate or united they are called polygamous. The flower that has stamens only is barren, because it produces neither fruit nor seed; the flower that bears the pistil is fertile. This may be understood by examining the flowers of the cucumber, melon, and gourd.

(e.) Plants, therefore, that have true flowers, i.e., having stamens and pistils, are phonogamous or flowering. Other plants are cryptogamous, such as fern, moss, sea-weed, &c. Their fructification consists of extremely minute vessels variously shaped and clustered. (Plate I. Fig. 8, 9, 10.)

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§ 3. Exogenous and Endogenous-Flowering plants are divided into two great classes, according to an accompanying difference in stem, leaf, seed, and also in the flower. (Plate I.)

(a.) The stem of an Exogenous plant is divided into pith, wood, and bark. (Fig. 1.) The pith is soft, occupying the centre, and sending out rays in every direction, which traverse the wood and terminate in the bark, and are called medullary

rays. The wood is formed in circles, each new one being outermost, and from this circumstance the stem derives its name exogenous, i.e., increased outwardly. The bark encloses the wood, and is increased by internal layers.

On the contrary, in the stem of an Endogenous plant the wood is in bundles, which are added towards the centre, i.e., increased inwardly. (Fig. 2.) Of the Exogenous structure we have abundant illustrations in every bush and tree of our country. To the Endogenous structure belong many tropical trees, occasionally cultivated in conservatories, such as the cocoa, palm, and plantain. The only native illustrations are lily-like or grass-like plants, in which the peculiar structure of the stem, if any, is not so easily determined.

Exogenous plants are also called Dicotyledons, because the seed has two opposite cotyledons or germinal leaves. (Fig. 6.) Endogenous plants are Monocotyledons, the seed having only one cotyledon. (Fig. 7.)

(b.) The flowers differ principally in the proportional number of parts. Exogenous flowers have the different parts generally in 4 or 5, or any multiples of these, 8, 15, 20, &c. Endogenous flowers are usually in 3, 6, or 9 parts, and their multiples. Thus the crocus contains 6 floral leaves, and 3 stamens; the lily, 6 floral leaves, and 6 stamens; the flowering rush, 6 floral leaves, and 9 stamens; the iris has 3 outer floral leaves, 3 inner, 3 stamens, 3 styles, and a 3-celled ovary. On the contrary, the rose, an exogenous plant, has flowers divided by 4 or 5; flowercup in 5 divisions, 5 petals, 20 stamens, &c.

(c.) Another striking difference is in the leaf. The leaf of an exogenous plant has branched and netted veins. (Fig. 3.)

The

veins of an endogenous leaf are nearly parallel, and not being netted may be easily torn into strips. (Fig. 4, 5.) Of the former, the leaves of lilac, elder, elm, lime, and rose, are illustrations. Of the latter, the leaves of grass, lily, tulip, arum, &c.

Most of the British endogenous plants are herbaceous, that is, succulent and not shrubby; they may, however, be readily known by the peculiar veining of the leaves, and by the ternary structure of their flowers.

§ 4. Dichlamydea and Monochlamydec.—Exogenous plants are subdivided according to their floral envelopes.

(a.) Perianth. The leaves surrounding the stamens and pistils are called collectively the perianth. It is this vesture or clothing that is often beautiful in tint and curious in shape, forming what is popularly considered as the flower. If there be more than one whorl or row of floral leaves, a plant is Dichlamydeous, i.e., having a double vestment. If there be only one, a plant is Monochlamydeous. The inner whorl is called the corolla, and is generally very delicate and beautifully coloured. The outer whorl is called the calyx, and is generally green. The corolla and calyx are occasionally confounded, both being coloured and consisting of several whorls, as the globe ranunculus, the water lily, &c.

There is sometimes a kind of outer calyx, called an involucre, as in the mallow. Any other leaves differing from the common leaves of the plant, not arranged in whorls, but occurring singly about or beneath the flowers, are called bracts, as in marjoram, heal-all, &c.

N.B.-The summit of the stalk upon which the pistils, stamens, and perianth, are arranged, is called the receptacle or thala

mus. And the fleshy surface sometimes lying between the ovary and the calyx, occasionally assuming peculiar forms, is called the disc.

(b.) Monochlamydea. Perianth either single or wanting. Few plants under this division possess flowers of any striking beauty. The perianth is usually green, but is sometimes coloured. The most beautiful instances are the mezereon, persicaria, and sorrel. The elm is a fine tree, but does not produce attractive flowers. Many plants of this division are destitute of both calyx and corolla, the flowers being separated by small leaves, and are chiefly trees, such as the oak, hazel, willow, chesnut, pine, and yew.

(c.) Dichlamydec.-Perianth double, i.e., consisting of calyx and corolla. If the calyx consists of several pieces or small leaves, each is called a sepal. The several pieces of the corolla are called petals. If the petals are separate, the corolla is polypetalous; if they are combined, united into one piece, it is monopetalous. When the calyx or corolla consists of one piece, the divisions, if any, are called lobes or segments; or, if small and pointed, teeth.

N.B. As the subdivision of Dichlamydeous plants depends on the mode in which the calyx and the inner parts of the flower are attached, the following particulars require to be very carefully observed :

Perigynous. (Plate II. Fig. 8.) If the petals and stamens are united with the calyx, they are said to be perigynous, i.e., around the pistil. The rose, houseleek, apple, hawthorn, currant, willow-herb, and campanula, are striking illustrations.

Hypogynous. (Plate II. Fig. 7.) If the petals and stamens are free from the calyx, simply attached to the receptacle, or even

combined with the ovary, they are said to be hypogynous, i.e., under the pistil. Buttercup, poppy, wall-flower, primrose, and snap-dragon, are instances.

Superior. (Fig. 6.) If the calyx is combined with the ovary, so as to appear to originate above it, then it is said to be superior, and the ovary to be inferior.

Inferior. (Fig. 5.) If the calyx is free from the ovary, then it is inferior, and the ovary is superior.

These terms generally apply to parts of a flower appearing to originate above or below another, in relation to which, if above, they are superior, and if below, inferior.

§ 5. Thalamiflora. Calyciflora. Corolliflora.-Dichlamydeous plants are arranged in 3 divisions according to the distinctions explained in the last section.

(a.) Thalamiflorce.-Flowers having separate petals (polypetalous) which with the stamens are not attached to the calyx but to the thalamus or receptacle (hypogynous). The sepals of the calyx often fall off soon after the flowers expand, or may generally be easily detached, leaving the petals and stamens upon the receptacle. (Plate II. Fig. 9, 10.) This will be readily perceived in the buttercup, poppy, wall-flower, and violet.

(b.) Calyciflora.--Flowers with the corolla and stamens attached to the calyx. Some plants in this division have polypetalous flowers, as the rose, cinquefoil, and pea; others have monopetalous flowers, as the honeysuckle, valerian, and campanula. The stamens may be removed with the calyx, which is also sometimes attached to the ovary (superior).

(c.) Corolliflora.-Petals combined into one piece (monopetalous), and free from the calyx (hypogynous). The stamens