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  its place in the list should be taken by the cocoanut, the only esculent species common to the two worlds within the tropics which we have reason to suppose was carried or drifted across the Pacific in prehistoric times. Being a littoral tree, with fruit capable of enduring long exposure to salt water, its dispersion is not so surprising. The question is, in which direction the dispersion was effected; and that perhaps can never be determined. In his general list De Candolle includes the Cocos nucifera among the plants of old-world origin, with queries whether of the Indian archipelago, or of Polynesia. In his former treatise he inclined to the theory of a transmission westward from the Pacific coast of Central America: in the body of the present work, after full statements pro and con, he is disposed to reverse his former opinion. But, as the dispersion may have been mainly by natural agencies, the question may be relegated to another class of inquiries. The presumption arising from the fact that all other species of Cocos are American, may be offset by the asserted fact that, although the tree formed forests on the islands off Panama when these were first visited by Europeans, it would appear to have only recently reached the West Indies and the adjacent main. So useful a tree, if indigenous to one side of the isthmus, would have been transported to the other and to the islands beyond by the very earliest races of men. As to oceanic transport, judging from the charts, the drifting of cocoanuts from America to Polynesia by the great current south of the equator seems hardly more or less likely than the reverse by the return equatorial current north of it.

It would be well to give some account of our author's method of investigation and exposition, of the kind of evidence which are brought to bear upon the questions discussed, botanical, paleontological and archeological, historical and linguistic, each bringing some light of its own sort, and in their coincidence giving all the assurance of which such inquiries admit. It would be interesting to show, moreover, that although in most cases the continent or even the country from which each plant came to Europe, or in which it has been immemorially cultivated, has been fairly well ascertained, their origin or parentage has not. Only one-third of them are really known to botanists in a natural or wild state; and from this number subtraction may be made of such as have been detected only once or twice, and which may merely have run wild: the common tobacco-plant of the new world, and the bean of the old, are in this category. On the other hand, there are several which botanists confidently trace to indigenous originals from which the cultivated plant has undergone considerable alteration: of such are the olive, the vine of the old world, flax, and the garden poppy; and in America, the potato, the sunflower-artichoke, and the tomato. But we know not, and we probably never shall discover, the particular source or origin of the cereal grains of the old world, and of maize in the new; of sorghum and sugar-cane; of the pea, lentil, chick-pea, and peanut, and of the commmon white bean; of sweet-potato and yams; and nearly the same may be said of the peach, oranges and lemons, and of all squashes and pumpkins.

But we must conclude our brief review with a note upon two or three plants, the early history of which concerns our own country.

Phaseolus vulgaris, our common bean, ranks in De Candolle's table as one of the three esculent plants, the home of which, even as to continent, is completely unknown. Linné credited it to India, as he did our Lima bean also; but he took no pains to investigate such questions. This has been so generally followed in the books, that even the Flora of British India in 1879 admits the species, adding that it is not anywhere clearly known as a wild plant. But Alph. De Candolle, in his former work, had discarded this view, on the ground that it had no Sanscrit name, and that there was no evidence of its early cultivation in India or farther East. Adhering, however, to the idea that our plant was the Dolichos and the Phaseolus or Phaselos of the Greeks, and of the Romans in the time of the Empire, he conjectured that its probable home was in some part of north-western Asia. But recently, as "no one would have dreamed of looking for its origin in the new world," he was greatly surprised when its fruits and seeds were found to abound in the tombs of the old Peruvians at Ancon, accompanied by many other grains or vegetable products, every one of them exclusively American. In his present very careful article he admits that we cannot be sure that it was known in Europe before the discovery of America, and that directly afterwards many varieties of it appeared all at once in the gardens, and the authors of the time began to speak of them; that most of the related species of the genus belong to South America, where, moreover, many sorts of beans were in cultivation before the