1. Maniocs were cultivated by the natives of Brazil, Guiana, and the warm region of Mexico before the arrival of the Europeans, as all early travellers testify. In the West Indies this cultivation was, according to Acosta,[188] common enough in the sixteenth century to inspire the belief that it was also there of a certain antiquity. 2. It is less widely diffused in Africa, especially in regions at a distance from the west coast. It is known that manioc was introduced into the Isle of Bourbon by the Governour Labourdonnais.[189] In Asiatic countries, where a plant so easy to cultivate would probably have spread had it been long known on the African continent, it is mentioned here and there as an object of curiosity of foreign origin.[190] 3. The natives of America had several ancient names for the varieties of manioc, especially in Brazil,[191] which does not appear to have been the case in Africa, even on the coast of Guinea.[192] 4. The varieties cultivated in Brazil, in Guiana, and in the West Indies are very numerous, whence we may presume a very ancient cultivation. This is not the case in Africa. 5. The forty-two known species of the genus _Manihot_, without counting _M. utilissima_, are all wild in America; most of them in Brazil, some in Guiana, Peru, and Mexico; not one in the old world.[193] It is very unlikely that a single species, and that the cultivated one, was a native both of the old and of the new world, and all the more so since in the family _Euphorbiaceæ_ the area of the woody species is usually restricted, and since phanerogamous plants are very rarely common to Africa and America. The American origin of the manioc being thus established, it may be asked how the species has been introduced into Guinea and Congo. It was probably the result of the frequent communications established in the sixteenth century by Portuguese merchants and slave-traders.