Australia has, in common with Europe, a very common plant, the daisy (_Bellis perennis_). The same little flower is found in northern Asia, in some regions in Africa and South America, and where it occurs it climbs the mountains from the level of the sea up to the snow-limit. The little enchanter’s nightshade, the delicate Linnæa, the bittersweet, the bird’s knot-grass, the blue gentian, the dwarf birch, and the herbaceous willow, and several others, are indigenous both in Europe and North America. The common self-heal, the duckweed, and our reed grow in New Holland. The bog-moss covers the moors of Peru and New Granada, as well as those of the Hartz and of Dovrefjeld in Norway. The brownish Parmelia, which clothes all our walls in Germany, palings, and old trees, is no less present on the only ninety-year-old Yorullo in Mexico. The bluish bristle-grass, which is one of the commonest garden and field weeds on sandy soils with us, grows also in the interior of Brazil on suitable soil. A characteristic plant of the seashores of Northern Europe and the vicinity of salt-springs, _Ruppia martima_, grows equally on the northern coast of Germany, in Brazil, and the East Indies. But it is needless to accumulate examples, for these so hasten to present themselves that the view finds some support in observation which assumes that every plant must exist in every part of the globe where the known conditions of its vegetation are present. The little daisy (_Bellis perennis_) exhibits a certain wilfulness. It is wanting all through North America; and that which we tread down as an insignificant weed in our European meadows is there reared with the most tender care in the botanical gardens. If we pass in review the vegetation of different countries, we see that causes appearing similar in our present knowledge of them bring forth indeed _similar_, but by no means the same, forms of plants. To the plants of a particular northern latitude correspond in the analogous height of the Alps, situated southward, other species of the same genera, or other genera of the same family; or the plants of America are represented in the same latitudes in the Old World by plants which are different, but closely allied, in their development. Nay, even plants which belong to totally different families assume, at least in their outward appearance, similar shapes. Thus the cactus plants of the New World correspond to the leafless, fleshy spurges of the torrid Africa.