In other cases the dispersion is mainly the work of the seed itself. In some of the lower plants, as, for instance, in many sea-weeds, and in some allied fresh-water plants, such as Vaucheria, the spores[5] are covered by vibratile cilia, and actually swim about in the water, like infusoria, till they have found a suitable spot on which to grow. Nay, so much do the spores of some sea-weeds resemble animals that they are provided with a red “eye-spot,” as it has been called, which, at any rate, seems so far to deserve the name that it appears to be sensitive to light. This mode of progression is, however, only suitable to water plants. In much more numerous cases, seeds are carried by the wind. In other instances, the plants themselves, or parts of them, are rolled along the ground by the wind. An example of this is afforded, for instance, by a kind of grass (Spinifex squarrosus), in which the mass of inflorescence, forming a large, round head, is thus driven for miles over the dry sands of Australia until it comes to a damp place, when it expands and soon strikes root. So, again, the Anastatica hierochuntica, or “Rose of Jericho,” a small annual with rounded pods, which frequents sandy places in Egypt, Syria, and Arabia, when dry, curls itself up into a ball or round cushion, and is thus driven about by the wind until it finds a damp place, when it uncurls, the pods open and sow the seeds. These cases, however, in which seeds are rolled by the wind along the ground, are comparatively rare. There are many more in which seeds are wafted through the air. Another mode, which is frequently adopted, is the development of long hairs. Sometimes, as in Clematis, Anemone, and Dryas, these hairs take the form of a long, feathery awn. In others the hairs form a tuft or crown, which botanists term a pappus. Of this the dandelion and John Go-to-bed-at-noon, so called from its habit of shutting its flowers about midday, are well-known examples. Tufts of hairs, which are themselves sometimes feathered, are developed in a great many Composites, though some, as, for instance, the daisy and lapsana, are without them; in some very interesting species, of which the common Thrincia hirta of our lawns and meadows is one, there are two kinds of fruits, one with a pappus and one without. The former are adapted to seek “fresh woods and pastures new,” while the latter stay near the parent plant and perpetuate the race at home. In other cases seeds are wafted by water. Of this the cocoanut is one of the most striking examples. The seeds retain their vitality for a considerable time, and the loose texture of the husk protects them and makes them float. Every one knows that the cocoanut is one of the first plants to make its appearance on coral islands, and it is, I believe, the only palm which is common to both hemispheres.