Some other plants bear a far more important share in the nutrition of mankind than the grasses last named. Even in the most northern zone of the barley and rye, the buckwheat is an object of tolerably extensive culture. With the already named banana, the yams, the manioc, and the batatas contribute largely to the daily food of the inhabitants of the tropics, of the Old as of the New World, added to which the Andes presents itself a peculiar vegetable, the quinoa, a plant which simultaneously produces edible tubers and abundance of seeds, comparable to those of buckwheat. Lastly, we may not pass over the _Bread-fruit_, in the proper sense of the word, which is the principal food of the inhabitants of the large islands which extend from the East Indies through the whole tropical ocean to the west coast of America, the gift of a large and beautiful tree of the family of the nettle, which from the use it is turned to is called the bread-fruit tree. For the sake of variety, some also cultivate with it the tarroo-root, the _Tacca_ tubers, or some ferns, the farinaceous leaf-stalks of which afford a dainty meal. Last of all I will mention the potato, which has spread over the whole earth with such rapidity from the mountains of the New World that in many places it threatens, not exactly to the advantage of mankind, to supplant every other culture. PHYSIOGNOMY OF PLANTS --ALEXANDER VON HUMBOLDT The carpet of flowers and of verdure spread over the naked crust of our planet is unequally woven; it is thicker where the sun rises high in the ever cloudless heavens and thinner toward the poles, in the less happy climes where returning frosts often destroy the opening buds of spring or the ripening fruits of autumn. Everywhere, however, man finds some plants to minister to his support and enjoyment. Lichens form the first covering of the naked rock, where afterward lofty forest trees rear their airy summits. The successive growth of mosses, grasses, herbaceous plants and shrubs or bushes, occupies the intervening period of long but undetermined duration. The part which lichens and mosses perform in the northern countries is effected within the tropics by Portulacas Gomphrenas and other low and succulent shore-plants. The history of the vegetable covering of our planet, and its gradual propagation over the desert crust of the earth, has its epochs as well as that of the migrations of the animal world.