CASSAVA is the name given to the farinaceous root stocks of two species of Euphorbiaceous plants, the Bitter Cassava, Manihot utilissima, and the Sweet Cassava, Μ. Aipi, both highly important sources of food starches. The plants are natives of South America, but the Bitter Cassava, which is the most important of the two in an economic sense, has been introduced into most tropical regions, and is extensively cultivated in the East Indian Archipelago, from which, as well as from Brazil and other South American states, its starch in the form of tapioca is a staple article of export. The Bitter Cassava root is fusiform, sometimes attaining a length of 3 feet and a weight of about 30 ft> Its sap contains hydrocyanic acid, and being therefore highly poisonous, the root cannot be eaten in a fresh condition; while on the other hand the Sweet Cassava is perfectly innocuous, and is employed as a table vegetable. Exposure to heat dissipates the poisonous principle, and the concentrated juice is in that state used as the basis of Cassareep and other sauces. From the Bitter Cassava roots many different food preparations are made in Brazil. The roots are preserved for use by being simply cleaned, sliced, and dried; from such dried slices manioc or cassava meal used for cassava cakes, <fcc., is prepared by rasping. The starch also is separated and used for food under the name of Brazilian arrowroot; and this, when agglomerated into pellets on hot plates, forms the tapioca of commerce. Cassava starch has a stellate hilum, which readily distinguishes it under the microscope from other starches. Its microscopic appearance is figured under Arrowroot, vol. ii. p. 631, fig. 6.