A dry mixed soil is best suited to its culture. So exhausting is this crop, that it cannot be raised more than two or three times successively on the same land. The roots arrive at maturity in eight or nine months after planting, but may be kept in the ground a much longer time without injury. Sweet cassava might be sliced, dried in the sun, and sent to Europe in that state. In dry weather the process succeeds remarkably well, and the dried slices keep for a considerable time. Dr. Shier ascertained that when these sliced and dried roots were first steeped and then boiled, they return to very nearly their original condition, and make an excellent substitute for the potato.
The plant thrives on even the poorest soil; the mode of planting is simple. It consists in laying cuttings a foot long in square pits a foot deep, and covering them with mould, leaving the upper ends open. From two to four pieces may be placed in each square. The planting ought to be in the rainy season. The cuttings must be made from the full-grown stem. A humid soil causes the root to decay, a dry soil is therefore more adapted for its cultivation. As blossoms are occasionally plucked from potato plants, so the manihot or cassava is deprived of its buds to increase the size of its roots. The raw root of the bitter species, when taken out of the ground, is poisonous—if exposed, however, to the sun for a short time, it is innocuous, and when boiled is quite wholesome.
The starch of the root of the manioc is prepared in the following manner, as described by Dr. Ure:—" The roots are washed and reduced to a pulp by means of a rasp or grater. The pulp is put into coarse strong canvas bags, and thus submitted to the action of a powerful press, by which it parts with most of its noxious juice. As the active principle of this juice is volatile, it is easily dissipated by baking the squeezed cakes of pulp upon a plate of hot iron. The pulp thus dried concretes into lumps, which become hard and friable as they cool. They are then broken into pieces, and laid out in the sun to dry. In this state they are a wholesome nutriment. These cakes constitute the only provisions laid in by the natives, in their voyages upon the Amazon. Boiled in water, with a little beef or mutton, they form a kind of soup similar to that of rice.
The cassava cakes sent to Europe are composed almost entirely of starch, along with a few fibres of the ligneous matter. It may be purified by diffusion in warm water, passing the milky mixture through a linen cloth, evaporating the straining liquid over the fire, with constant agitation. The starch, dissolved by the heat, thickens as the water evaporates, but on being stirred it becomes granulated, and must be finally dried in a proper stove.
2. Bitter cassava (Janipha Manihot, of Kunth; Jatropha Manihot, of Linnæus; and Manihot utilissima, Pohl).—This species has a knotty root, black externally, which is occasionally 30 lbs. in weight. In the root there is much starchy matter deposited, usually along with a poisonous narcotic substance, which is said to be hydrocyanic acid. The juice of the plant, when distilled, affords as a first product a liquor which, in the dose of thirty drops, will cause the death of a man in six minutes. It is doubted whether this acid pre-exists in the plant; some suppose it to be generated after it is grated down into a pulp. It can be driven off by roasting, and then the starch is used in the form of cassava bread. It is principally from the starch of the bitter cassava that tapioca is prepared by elutriation and granulating on hot plates. This serves to agglutinate it into the form of concretions, constituting the tapioca of commerce. This being starch very nearly pure, is often prescribed by physicians as an aliment of easy digestion. A tolerably good imitation of it is made by beating, stirring, and drying potato starch in a similar way.
The grated starch of the roots, floated in water, is spontaneously deposited, and when repeatedly washed and dried in the sun, forms cassava flour, called "Moussache" by the French.
The juice of the bitter cassava, mixed with molasses and fermented, has been made into an intoxicating liquor, which is much relished by the negroes and Indians.
The concentrated juice of the bitter cassava, under the name of cassareep, forms the basis of the West India dish, "pepper pot." One of its most remarkable properties is its highly antiseptic power, preserving meat that has been boiled in it for a much longer period than can be done by any other culinary process. Cassareep was originally an Indian preparation.
The manioc or cassava is cultivated in America, on both sides of the equator, to about latitude 30 degrees north and south. Among the mountains of intertropical America, it reaches to an elevation of 3,200 feet. It is cultivated also in great abundance on the island of Zanzibar, and among the negro tribes of Eastern Africa to the Monomoesy, inclusive; on the west coast of Africa, in Congo and Guinea. It appears not to have been introduced into Asia. The farina of the manioc is almost the only kind of meal used in Brazil, at least in the north, near the equator. An acre of manioc is said to yield as much nutriment as six acres of wheat. Meyen states, "It is not possible sufficiently to praise the beautiful manioc plant." The Indians find in this a compensation for the rice and other cerealia of the Old World. It has been carried from Brazil to the Mauritius and Madagascar.
The following quantities of Brazilian arrowroot, or tapioca, were imported in the undermentioned years:—