It is known by various local names—such as mani manoti by the Spaniards, and has obtained also that of cacahuete in some countries. It has the additional term hypogea attached to it, which literally signifies subterranean. This is apt to mislead; for the plant grows above ground as other pulse, whereas only its seed and pericarp are inserted, after blooming, into the earth. Hence the better term hypocarpogea.
It appears to form an important article of cultivation along the whole of the west coast of Africa, and probably on the east coast, on several parts of which it was found by Loureiro ("Flor. Cochin," p. 430). It was doubtless carried from Africa to various parts of equinoctial America, for it is noticed in some of the early accounts of Peru and Brazil. 800 quarters of this nut were imported into Liverpool from the West Coast of Africa, in 1849, for expressing oil, and about half that quantity in 1850.
Eighty to 90 tuns of the expressed oil are now annually imported. The seeds contain about 44 per cent. of a clear pale yellow oil, which is largely used in India as food, and for lamps, particularly at Malwa and Bombay, &c. Two varieties are grown in Malacca, the white seed and the brown seed, and also in Java, in the vicinity of sugar plantations; the oil cake being used as manure. It is there known as katjang oil.
This plant, which seems to be a native of many parts of Asia, has within the last ten years been much cultivated about Calcutta. The seeds contain abundance of fixed oil, have a faint odor, and very mild agreeable taste; 1,950 parts of seed, separated from their coverings and blanched, give 1,405 of kernels, from which, by cold pressure, 703 parts of oil are procured. The seeds are consumed as a cheap popular luxury, being half roasted, and then eaten with salt. The oil is calculated to serve as an efficient and very cheap substitute for olive oil, for pharmaceutical purposes. It burns with little smoke, with a clear flame, and affords a very full bright light, answering perfectly in Argand lamps.
The oil cake affords, also, an excellent food for cattle.
The ground nut has of late become of considerable importance as an article of exportation, by English houses; yet more so by French houses at Ghent, Rouen, and Bordeaux; some of whom have contracted with the merchants of the African colonies for large quantities, sending shipping for the cargoes. One house alone contracted for 60,000 bushels in the years 1844 and 1845. This nut oil is so very useful to machinery that the naval steam cruisers on the coast have adopted it. A ground-nut oil factory exists in the colony of Sierra Leone; but from the want of steam power and proper machinery, and from bad management, together with the inferior attainments of the African artisan, when compared with the European mechanic, and their facilities in quantity or quality, there is abundant scope for improvement. The price in the colony is 4s. 6d. per gallon. It is capable of being refined so as to answer the purpose of a salad oil; the nut is prolific, and eaten by the natives and Europeans, boiled, roasted, or in its raw state; and frequently introduced at the table as we do the Spanish Barcelona nut at dessert. It grows in the rainy season, and is collected in the dry, and sold in the colony for one shilling to eighteen-pence per bushel, in goods and cash. Form of the nut, long, light shell, contains two kernels covered with a brown rind, when shelled white in appearance.
It is a low creeping plant, with yellow flowers; after they drop off, and the pods begin to form, they bury themselves in the earth, where they come to maturity. The pod is woody and dry, containing from one to three peas, or nuts, as they are called, hence the common names, ground-nut or pea-nut. They require to be parched in an oven before they are eaten, and form a chief article of food in many parts of Africa.
From a narrow strip of land, extending about 40 miles northerly from Wilmington (North Carolina), comes nearly the entire quantity of earth nuts (known as pea-nuts) grown in the United States for market. From that tract and immediate vicinity, 80,000 bushels have been carried to Wilmington market in one year.
The plant has somewhat the appearance of the dwarf garden-pea, though more bushy. It is cultivated in hills. The pea grows on tendrils, which put out from the plant and take root in the earth, where the nut is produced and ripened. The fruit is picked from the root by hand, and the vines are a favorite food for horses, mules, and cattle. From 30 to 80 bushels are produced on an acre. There are some planters who raise from 1,000 to 1,500 bushels a year.—("Hunt's Merchant's Magazine," vol. xv., p. 426.)
The ground-nut is exceedingly prolific, and requires but little care and attention to its culture, while the oil extracted from it is quite equal to that yielded by the olive. Almost any kind of soil being adapted for it, nothing can be more simple than its management. All that is required is the soil to be turned over and the seed sown in drills like potatoes; after it begins to shoot it may be earthed with a hoe or plough. In many parts of Western Australia they are now grown in gardens for feeding pigs, the rich oil they are capable of yielding being entirely overlooked. In regard to their marketable value at home, I will give a copy of a letter of a friend of mine, received from some London brokers, largely engaged in the African trade:—