CASSAVA. Manihot utilissima, Pohl. (Jatropha Manihot, Linn. Janipha 4lanihot, H. B. K.). Euphorbiaceee. Cassava (U. S.), manioc, mandioca, aypi, yuca, and others (S. Amer. ), tunglu-bok, simul-alu, tan-u, and others (India). Figs. 323, 324.
A shrubby plant, perennial in the tropics but annual in temperate regions, cultivated for its fleshy roots which are used for the manufacture of starch, Brazilian arrow-root and tapioca, for feeding domestic animals, and for the table. The cultivated forms are not known in a wild condi tion, but are undoubtedly natives of the American tropics.
The cultivated form is a shrub three to ten feet in height, the stem and branches forking regu larly in threes, with long-petioled, palmately parted leaves having usually five to nine divisions reaching nearly to the base, the sections being entire and elliptical or spatulate in outline. The growing plant bears a strong resemblance to the castor-bean (ricinus), to which it is closely related. The valuable part of the plant is its cluster of fleshy roots, which have a resemblance to the sweet-potato, though often reaching six or eight feet in length.
While two species have been described as the original types of the cultivated form of cassava— the "bitter," Manihot utilissima, Pohl., containing a considerable quantity of hydrocyanic acid, and the "sweet," Manihot Aipi, Pohl, containing little of the poisonous acid,—recent investigations indi cate that all the cultivated forms have been developed from a single stock, probably the .1/. Aipi. Careful structural and chemical examina tions of a very large number of cultivated forms from Ecuador, Colombia and the West Indies, includ ing both sweet and bitter sorts, show no constant differences. In different varieties the color of the root may vary from dark red to light yellow or almost white, while the stems and petioles show equal variations, hut either of these characters may change in the first generation when plants are grown from seeds. The roots of all varieties contain some hydrocyanic (prussic) acid, the quantity varying from a mere trace in some of the sweet varieties to as much as .03 per cent in
some of the so-called "bitter" sorts; but the quan tity in any variety, even when grown from cut tings, varies greatly with seasons, soils and climates. So far as is known, all varieties grown in the United States contain so little of the acid as to be harmless, and the same is said to be true of the sorts grown in India. The most poisonous varieties often cause death a few minutes after being eaten raw, but become perfectly harmless when cooked or dried, and even when pulped and exposed a few hours to the heat of the sun.
History.
Cassava was in common use in tropical America when the country was first explored by the Spaniards, and was introduced into western Africa in the sixteenth century, and into southern Asia a little later. There is no record of its introduc tion into the United States, hut it was abundant in Florida as early as 18(30, and was in common use there during the civil war as a source of starch. It gradually came into use for the feeding of live stock, and, between 1895 and 1900, establishments for the manufacture of starch on a commercial basis were opened in that state. The area of its cultivation for feeding purposes has been extended gradually westward, and it is now becoming com mon as far west as Texas.
Culture.
The plant requires a light, sandy and fairly fertile soil for its best success. While it produces abundantly on heavy soils, the digging of the roots is too expensive for profit. Some varieties make a vigorous growth where the annual rainfall does not exceed twenty inches, while others endure as much as 200 inches without injury. Some varieties mature within six months from planting, while others require two years before they are ready for gathering. The sweet varieties are usually more hardy, mature more quickly and yield less abundantly than the bitter sorts.