The slender-rooted variety grows wild in sandy soil, and especially near the sea in the Canary Isles, and all along the coasts of the Mediterranean Sea, and as far as the Caspian Sea, Persia, and Babylon,[174] perhaps even as far as the west of India, whence a specimen was brought by Jaquemont, although it is not certain that it was growing wild. Roxburgh’s Indian flora, and Aitchison’s more recent flora of the Punjab and of the Sindh, only mention the plant as a cultivated species.
It has no Sanskrit name,[175] whence it may be inferred that the Aryans had not brought it from western temperate Asia, where it exists. The nations of Aryan race who had previously migrated into Europe probably did not cultivate it, for I find no name common to the Indo-European languages. The ancient Greeks, who used the leaves and roots, called the species teutlion;[176] the Romans, beta. Heldreich[177] gives also the ancient Greek name sevkle, or sfekelie which resembles the Arab name selg, silq,[178] among the Nabatheans. The Arab name has passed into the Portuguese selga. No Hebrew name is known. Everything shows that its cultivation does not date from more than three or four centuries before the Christian era.
The red and white roots were known to the ancients, but the number of varieties has greatly increased in modern times, especially since the beetroot has been cultivated on a large scale for the food of cattle and for the production of sugar. It is one of the plants most easily improved by selection, as the experiments of Vilmorin have proved.[179]
Manioc—Manihot utilissima, Pohl; Jatropha manihot, Linnæus.
The manioc is a shrub belonging to the Euphorbia family, of which several roots swell in their first year; they take the form of an irregular ellipse, and contain a fecula (tapioca) with a more or less poisonous juice.
It is commonly cultivated in the equatorial or tropical regions, especially in America from Brazil to the West Indies. In Africa the cultivation is less general, and seems to be more recent. In certain Asiatic colonies it is decidedly of modern introduction. It is propagated by budding.
Botanists are divided in opinion whether the innumerable varieties of manioc should be regarded as forming one, two, or several different species. Pohl[180] admitted several besides his Manihot utilissima, and Dr. Müller,[181] in his monograph on the Euphorbiaceæ, places the variety aipi in an allied species, M. palmata, a plant cultivated with the others in Brazil, and of which the root is not poisonous. This last character is not so distinct as might be believed from certain books and even from the assertions of the natives. Dr. Sagot,[182] who has compared a dozen varieties of manioc cultivated at Cayenne, says expressly, “There are maniocs more poisonous than others, but I doubt whether any are entirely free from noxious principles.”
It is possible to account for these singular differences of properties in very similar plants by the example of the potato. The Manihot and Solanum tuberosum both belong to suspected families (Euphorbiaceæ and Solanaceæ). Several of their species are poisonous in some of their organs; but the fecula, wherever it is found, is never harmful, and the same holds good of the cellular tissue, freed from all deposit; that is to say, reduced to cellulose. In the preparation of cassava, or manioc flour, great care is taken to scrape the outer skin of the root, then to pound or crush the fleshy part so as to express the more or less poisonous juice, and finally the paste is submitted to a baking which expels the volatile parts.[183] Tapioca is the pure fecula without the mixture of the tissues which still exist in the cassava. In the potato the outer pellicle contracts noxious qualities when it is allowed to become green by exposure to the light, and it is well known that unripe or diseased tubers, containing too small a proportion of fecula with much sap, are not good to eat, and would cause positive harm to persons who consumed any quantity of them. All potatoes, and probably all maniocs, contain something harmful, which is observed even in the products of distillation, and which varies with several causes; but only matter foreign to the fecula should be mistrusted.
The doubts about the number of species into which the cultivated manihots should be divided are no source of difficulty regarding the question of geographic origin. On the contrary, we shall see that they are an important means of proving an American origin.
The Abbé Raynal had formerly spread the erroneous opinion that the manioc was imported into America from Africa. Robert Brown[184] denied this in 1818, but without giving reasons in support of his opinion; and Humboldt,[185] Moreau de Jonnes,[186] and Saint Hilaire[187] insisted upon its American origin. It can hardly be doubted for the following reasons:—