While many plants and trees may be propagated by branches, buds, suckers, and leaves fixed in the ground; so concerning the dissemination of seeds after they come to maturity, the Author of nature has wisely provided in various ways; this being absolutely necessary, since without it no crop could follow. The stalks and stems favor this purpose; for these raise the fruit above the ground, so that the winds, shaking them to and fro, widely disperse the ripe seeds. The pericarpium, a pellicle or thin membrane encompassing the fruit or grain of a plant, is generally shut at the top, that the seeds may not fall before they are shaken out by stormy winds. Wings are given to many seeds, by the help of which they fly far from the mother plant, and frequently spread over a large tract of country. These wings consist either of down, as in most of the composite-flowered plants; or of a membrane, as in birch, alder, ash, &c. Several kinds of fruits are endued with a remarkable elasticity, by the force of which the ripe pericarpies throw the seeds to a great distance; as wood-sorrel, spurge, phyllanthus, and dittany. Other seeds or pericarpies are rough, or provided with hooks, as hounds-tongue, agrimony, &c; so that they are apt to stick to animals which pass by them, and by this means are carried to their holes, where they are both sown and manured. Berries, as well as other pericarpies, are by nature allotted for aliment to animals; but, with this condition, that while they eat the pulp, they shall sow the seeds: for when they feed on it, they either disperse them at the same time; or, if they swallow them, they are returned unhurt. The mistletoe always grows on other trees, because the thrush eating its seeds, casts them forth with its dung. The cross-bill living on fircones, and the haw-finch feeding on pinecones, sow many of their seeds.