being to form a protective envelope for the other organs of the flower. Within the calyx, we descry the corolla (Fig. 208, co). This is the circle of petals or leaves which, par excellence, we call the "flower," because it constitutes in the vast majority of flowers the bright and showy portion thereof. A flower might botanically or physiologically be perfect enough minus its corolla; al

though the eye, missing the bright petals, would be apt to regard such a plant as wanting the first and chiefest element of the blossom. The common nettle, for instance. appears to possess no "flowers" in the popular and accus

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FIG. 209.-NETTLE-FLOWERS.

tomed sense of the term; but when we examine the plant, we readily discover that it possesses parts corresponding to the flowers (Fig. 209) of other plants. In the greater nettle, the flowers of one plant are essentially different (in that they possess "stamens" (Fig. 209 s s) alone)

FIG. 210.-FEMALE OR PISTILLATE
FLOWERS OF WILLOW.

FIG. 211.-MALE OR STAMINATE
FLOWERS OF WILLOW.

from those of another plant (which possess "pistils" (p) only). But in the lesser nettle, or in the oak, these distinct flowers (Figs. 212, 213) are found on one and the same plant. No vestige of colour appears in either, however; and when we study the flowers in question, we

find that a corolla is wanting, although a calyx (Fig. 209, c) is present. Again, in the willow, which, like the greater nettle, has its stamens and pistils (Figs. 210 and 211) on different plants, there appears to be no "flower" in the ordinary sense of the term; and the calyx as well as the corolla is found to be wanting in these trees.

The stamens, just mentioned, form the third set of organs proper to the perfect flower. Looking at buttercup, wall-flower (Fig. 205, st), saxifrage (Fig. 215) or campanula (Fig. 214), we readily see the stamens. They exist as stalked organs (Fig. 214, ss), each con

FIG. 212.-MALE OR STAMINATE FLOWERS OF OAK.

sisting of a stalk or filament (Figs. 216, 217, st), and a head called the anther (a). The head is hollow and contains the fine yellow dust termed pollen, which, at the time of ripening, is usually found scattered conspicuously about the interior of most flowers. The fourth and central set of organs found in the flower constitute the pistil (Figs. 214, 215, and 218) or seed-producing structure. This organ is composed of one or more parts called carpels. Each carpel consists in turn of a lower distended part called the ovary (Fig. 218, ov), within which the ovules are produced; of a neck or filament, the style (st); and of a head borne on the style (sg), and named the stigma. The style or stigma may be absent; but in the great majority of flowers both parts are present, the ovary being

however, the essential part of the pistil. In the "head" of a poppy, for instance, there is no style; the bulk of the "head" consisting of the ovary containing numerous seeds, and the flat cap or lid representing the "stigma" of the poppy-pistil. As a final observation concerning the parts of the flower,

it may be noted that the separate pieces, or "carpels," of which a pistil is composed, may either be free and distinct, or closely united and adherent to each other; whilst a second fact of importance in the general description of flower structure, consists in the declaration that the ripe and mature pistil is the fruit in botanical parlance. True, there may, as in the strawberry (Fig. 219), be found united to the ripe pistil certain other parts

which constitute the edible and FIG. 213.-PISTILLATE FLOwers of Oak. desirable portion of the plant. The

true pistil in the strawberry consists of the little yellow carpels, (Fig. 219, f), usually called "seeds," which are imbedded in the fleshy mass of the fruit formed by the expanded top of the flower-stalk. But the æsthetics of taste must be neglected in the strict descriptions

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FIG. 214.-PARTS OF A FLOWER (CAMPANULA).

FIG. 215.-FLOWER OF SAXIFRAGE
IN SECTION.

of science; and that alone is the "fruit," in the eyes of the botanist, which is formed by the ripened pistil, or central organ of the flower.

All parts of the flower, it must be observed, are not of equal value in the eyes of the botanist., Those organs-stamens and pistil-which produce and elaborate the seed, are physiologically more important

than the circlets or whorls of leaves which, in the form of calyx anď corolla, surround and protect them. Yet the latter organs play their own part in the production of seeds, and in some cases serve as the actual means whereby special modes of fertilisation are primarily induced and carried out. As the sequel may show, indeed, the

calyx and corolla-which in previous years were deemed mere "floral envelopes," being credited, as such, with a merely protective function-have largely risen in importance in the estimation of the

botanical world; since on the form, colour, size, &c., of the corolla especially, largely depend the working of those mutual relations which have been formed between the insect-world on the one hand, and the world of flowers on the other. Peculiarity of a corolla implies, botanically, as a rule, peculiarity of fertilisation; and the importance of the blossom becomes plainly apparent FIG. 219.—STRAWBERRY. to us when we discover that in place of the somewhat limited function formerly assigned to it by the unscientific philosopher-namely, that of affording delight to man by its beauty-it subserves the truer and more logical mission of aiding materially the increase of the race to which it belongs, and of which it forms such a characteristic part.

Turning to the primrose for practical illustration of the foregoing

precepts, we may readily enough find in its structure plain instruction in the build of the flower. The circle of green leaves placed outside the yellow blossom is, of course, the calyx. This green cup consists of five leaves or sepals united in the primrose, but free and easily separable in the buttercup or wallflower (Fig. 205, A, ca). The blossom or corolla (Fig. 208, co) of the primrose exhibits similarly a united condition of parts. We can tell that it consists of five petals, or leaves, by counting its prominent lobes or projections. When we tear the corolla in two, longwise, we readily perceive the five stamens (a), which, however, in the primrose, exhibit a somewhat peculiar position, in that, instead of arising from the end of the flower-stalk, like the other organs of the flower, they spring from the sides of the united petals (Fig. 208). If we seize the corolla of a primrose by its upper portion, and pull it gently upwards, the entire blossom with its attached stamens will become detached from the flower-stalk, leaving the calyx and pistil on the latter organ. Then tearing or cutting away the calyx, we may be favoured with a clear view of the pistil itself, seated on the extremity of the flower-stalk. In the pistil (Fig. 218) we behold a body consisting below of the swelled or rounded structure already mentioned, and named the ovary (ov). This being cut across, is seen to contain numerous seeds or ovules, as the case may be, arranged around a central pillar named the placenta. From the upper part of the ovary arises a long stalk, the style (st) of the pistil; and the style, in its turn, is capped by a flat head, the stigma (sg). In the pistil of the primrose we therefore see the three typical parts, already noted as constituting the central organ of the flower. The pistil in this case, it may be remarked, consists of five carpels, so closely united that it is only by the aid of the "law of symmetry" (or that demonstrating the general correspondence of numbers in the flower-parts) that we can determine its composition. Five is the ruling number in the calyx, corolla, and stamens. Hence we conclude that the pistil of the primrose in its composition will conform to the type of the other whorls of the flower.

The physiology of the flower naturally follows the consideration of its structure. Living action, in other words, forms the natural corollary to living machinery or structure; hence we may fitly inquire into the manner in which the work of fertilisation is carried on in the economy of the primrose. Leaving for after treatment, the more special features of fertilisation, the general scope of the function whereby, as we have seen, the immature "ovules" are converted into "seeds "- each capable of developing, when planted, into a new primrose-may be readily appreciated. The stamens, each possessing as its essential part the anther or head (Figs. 216 and 217, a), develop the yellow dust, or pollen, as one of the two elements concerned in the work of plant-development and repro