living in the palms, where, with mats coated with clay, they construct hearths for the fires which are essential to their comfort. In other districts the palm-groves, says Desfontaines, "being impervious to the sun's rays, afford a hospitable shade, both to man and other animals, in a region which would otherwise be intolerable from the heat. Under this natural shelter the orange, the lemon, the pomegranate, the olive, the almond, and the vine, grow in wild luxuriance, producing, notwithstanding they are so shaded, the most delicious fruit. And here, while the eyes are fed with the endless variety of flowers which deck these sylvan scenes, the ears are at the same time ravished with the melodious notes of numerous birds, which are attracted to these groves by the shade, and the cool springs, and the food which they there find." The date, the cocoa-nut, and the sago palm, are of vast importance to mankind, for the nourishing farinaceous food they supply, and their extraordinary fecundity, which led to the assertion of Linnæus, that the region of palms was the first country of the human race, and that man is essentially palmivorous. The cocoa palm produces annually, during the greater part of a century, 100 of its large nuts, but the Seje palm of the Orinoco yields 8000 fruits at a crop. A single spatha of the date palm, the broad sheathing leaf which incloses the flowers, contains 12,000, while each spatha of another species, the Alfonsia Amygdalina, has 207,000 flowers, and the individual plant 600,000. The produce of the banana, or plantain, another inhabitant of tropical climes, is still more enormous; a plant which requires but little cultivation, and is to immense numbers of the human race, what rice is to the Hindoos, and wheat to the Europeans. According to a calculation of Humboldt, upon the same space of ground, the weight of the yield in the case of bananas will be 44 times that of potatoes, and 133 times that of wheat!

In thus proceeding through the vegetable kingdom from the pole to the equator, we come to different productions as we descend from the frozen to the cold, the temperate, the warm, and the hot regions; but as a change of elevation has the same effect upon climate as a change of latitude, the plants that are characteristic of the high latitudes appear in succession upon the lofty mountains of those that are much lower. Tournefort found the plants that are peculiar to Armenia at the foot of Mount Ararat; above these he met with those that are common in France; at a still greater height he came to those that grow in Sweden; and towards the summit the vegetation of the polar regions appeared. The Alps, Pyrenees, and Andes exhibit the same feature; and hence it may be regarded as a botanical axiom, that the flora of a mountainous country will be richer than that of another of less diversified aspect in the same latitude. The table states some interesting facts respecting vegetation on some of the mountains of the torrid and temperate zones. The fathom is equal to 6·39453 English feet.

Marine botany exhibits a similar diversity of species in different temperatures and localities of the ocean. The Polar Atlantic, the West Indian seas, the Indian Ocean and its gulfs, the eastern shores of South America, the coast of New Holland, the Mediterranean and Red seas, have each peculiar kinds of algae, or sea-weed, belonging to them, though some marine productions take a very wide range, and appear to be universally diffused. The genus fucus, which grows up to the surface from deeply sunk rocks, forming immense beds, which act as natural breakwaters, and appear like extensively inundated meadows, through which ships with difficulty can make their way, is found from the extreme southern islets near Cape Horn, along the whole western coast of South America, and in the tropical Atlantic Ocean. It is abundant in the northerly regions of the deep. This plant has already been mentioned as remarkable for the enormous length of its stems, in some cases reaching to three hundred and sixty feet. It is a striking example, also, of rapid growth. Mr. Stephenson found that a rock uncovered only at spring-tides, which had been chiselled smooth in November, was thickly covered with fucus digitatus two feet in length, and fucus esculentus six feet, in the following May, within six months afterwards. Some terrestrial plants, likewise, are extensively diffused, and adapt themselves to every variety of climate. The Samolus valerandi, a flowering marsh plant, occurs all over the globe, associated with the birches of the frozen north, and with the palms of the burning tropics.

But climate only suffices very partially to explain the phenomena of vegetable distribution; for under the same, or corresponding parallels of latitude, at the same elevations above the level of the sea, and upon kindred soils, we find totally distinct genera, and different species. The genus erica, or the common heath, seems to be exclusively confined to one side of our planet. It is chiefly to be found in a narrow longitudinal zone, extending from the northern parts of Europe to the Cape of Good Hope; for it rarely occurs in Asia, and of the 137 known species not one belongs to America. "Large commons without heaths," says Mr. Lyell, speaking of his first transatlantic impressions, in the neighbourhood of Boston, "reminded me of the singular fact that no species of heath is indigenous on the American continent." On the other hand, the cactus family belongs as exclusively to the New World as the heaths to the Old. The beautiful and fragrant rose-tree appears to be entirely wanting as a native plant in South America, ¦ and throughout the southern hemisphere; and in general, comparing the vegetation of the two continents, where the same genera recur, the species are not identical. Humboldt found upon the lofty mountains of equinoctial America, where the climate corresponds with that of the temperate zone, plantains, valerians, arenarias, ranunculuses, medlars, oaks, and pines, which, from their physiognomy, might be confounded with those of Europe, but they were all specifically different. The plants of New Holland, with very few exceptions, are different to those of the rest of the world; and of sixty-one native species, in the little island of St. Helena, only two or three are to be found in any other part of the globe. In some instances, upon travelling across a ridge of mountains, without any change of latitude, the vegetation is found quite different on the one side from the other. Nothing can be more striking than the contrast between the vegetation of the eastern and western sides of the chain of the Rocky Mountains. On the eastern side azaleas, rhododendrons, magnolias, with a variety of oaks and elms, form the principal features of the landscape; but beyond the ridge, most of these genera entirely disappear, and the giant pine becomes the chief object in view. Starting in an easterly direction through the northern parts of the Old World, we gradually lose the oak, the wild-nut,and the appletree, so common in Europe, upon crossing the Uralian mountains, and they cease to be met with beyond the banks of the Tobol; but in the eastern parts of Asia, on the banks of the Argouan, the two former occur anew, and the last re-appears in the Aleutian isles.