Within the flowers we saw, protected and shut in, the carpels or seed-box, within which are the very young structures which will become seeds. Now let us watch them develop. In such flowers as the sweet pea, for example, in summer-time, this will not take very long. Mark a special flower, and watch it each day; you will find the little green pod will gradually grow bigger, till it splits away the petals which are beginning to wither, and pushes out between them. As the pod gets larger you can see the seeds within growing too, if you look at the pod carefully against the light. The stigma does not grow any further, as its work was finished when it had caught the pollen grains. After a time the petals and stamens drop right away, and only the calyx remains; it does not grow very much, but it keeps fresh and green for some time, as it has still to act as a cup to hold the pod. It only takes a few days for these things to happen, then till the pea pod is quite ripe may take a week or two more. The pod continues to grow and turns yellowish brown and dry, then one day when the sun is warm you may see and hear it split open suddenly down its central ridge, and shoot out the brown, dry seeds. Then the work of the flower is quite over, and the seeds have started to make their own way in the world. [Illustration: Fig. 81. A, ripe carpel of pea or “pea pod.” B, pod suddenly split and twisted up, scattering the seeds.] Let us pick a nearly ripe pea-pod and examine it; it is the ripe carpel, with several ripe seeds in it, and together they form what is called a ~fruit~. In the case of the pod the “fruit” itself is a dry pea-pod husk, but in other plants the fruits may be very different. Examine a marrow, for example. Watch it in the course of its growth, if possible, and you will find that the marrow flower is one of those with its seed-box below and outside the calyx and petals. As the marrow ripens this swells with the food stored in it, and the many growing seeds, till the flowers are only small shrivelled structures at one end. If you then cut the ripe, or nearly ripe, marrow fruit across, you will find that its wall is very thick and fleshy, and that the many seeds are buried in a soft pulp. The melon shows us just the same thing. Such fruits seldom split suddenly to shoot out their seeds (though some foreign ones do); they depend more on animals which may eat them and so scatter the seeds about. In all cases it is better for the plant to have the seeds scattered so that they do not sprout too near together, but have room enough to grow without crowding each other out.