Once the act of pollination is effected, the duty of the petals and stamens is finished, and they generally fade. The sepals often remain, as in the Rose. By the growth of the pollen tube from the stigma into the ovary, fertilization is effected, and mature seed is produced. The fruit--that is, the seed and its coverings or appendages--offers the most varied forms of any of the plant organs--compare Hazel, Strawberry, Pea, Apple, Cranesbill, Dandelion; the variety is endless. Many of these forms are connected with the means by which seed-dispersal is effected: this subject has been touched on in Chapter III. But in numerous instances we can no more assign a reason for their beautiful or fantastic forms than we can account for the infinite variety of shape assumed by leaves and flowers. Summing up, then, what has been sketched in this chapter, we must think of our plant as a very complicated and wonderful machine, of which the terrestrial Seed Plant is the highest expression. Water is the basis on which its activities are founded--the currency in which all business is transacted. The amount of water contained in a growing plant is seldom realized. Even solid timber, when growing, is half wood, half water. A fresh lettuce loses 95 per cent. of its weight if the water is driven off by drying. Living in an aerial medium which tends to deprive it of moisture continually, and which furnishes water to the soil only intermittently in the form of rain, and often in sparing quantity, the plant envelops itself from end to end of its exposed portions in a waterproof cuticle; the only openings in its surface layer are the spongy tips of the root hairs on the one hand, and in the stomata on the other. These minutest of openings--so small that the number on a square inch of leaf surface often far exceeds a hundred thousand--might prove danger-points were they not most jealously watched over. But each is provided with a pair of guard-cells ready to close the opening at any moment; and where drought threatens, the whole of the stomata are found in concealed positions. An ample pipe-system extends from root, through stem, to leaf, but it does not communicate directly with the openings at either end. All material, whether liquid or gaseous, absorbed or given out, has to run the gauntlet of the living cells, which are jealous watchmen, and allow only selected substances to pass through them. The crude building materials and food materials are assembled in the leaves, where in cells spread out to the light the chlorophyll is massed. Under the microscope, the chlorophyll is seen to be located in minute granules embedded in the semifluid contents of the cells. Well may we gaze in wonder at these tiny green specks. Each is so small that although a couple of hundred of them are often present in each cell, they occupy but a very small proportion of its volume. The cells themselves are of microscopic size. The chlorophyll itself occupies only quite a small