Arrowroot is distinguished by the granules agglomerating into small balls, by slightly crepitating when rubbed between the fingers, and by yielding with boiling water a fine, transparent, inodorous, and pleasant-tasted jelly. In microscopic structure the granules present an ovoid form, marked with concentric lines very similar to potato-starch, but readily distinguished by having a “hilum” marking at the thick extremity of the granule, while in potato-starch the same appearance occurs at the thin end (compare figs. 3 and 4 below). In addition to the West Indian supplies, arrowroot is now found in the commerce of Brazil, the East Indies, Australia, Cape Colony, and Natal, in the last of which localities it has become a staple of some importance. Bermuda arrowroot has always been held in the highest esteem, but on those islands the cultivation is gradually giving way to more profitable crops. In 1872 only 26,710 lb, of the value of £1323, were exported from the Bermudas, while in 1851 the value of the export trade was more than £10,000. St Vincent is now the chief seat of arrowroot culture in the West Indies.

Tous-les-mois, or Tulema arrowroot, is obtained from several species of Canna, a genus closely allied to Maranta, and cultivated in the same manner. The granules of tous-les-mois are readily distinguishable by their very large size (fig. 5). East Indian arrowroot is obtained from the root-stocks of several species of the zingiberaceous genus, Curcuma, chiefly C. angustifolia. Brazilian arrowroot is the starch of the cassava plant, Jatropha Manihot (fig. 6), which when agglutinated on hot plates forms the tapioca of commerce. The cassava is now cultivated in the East Indian Archipelago as well as in South America. Tacca, or Otaheite arrowroot, is the produce of Tacca pinna-tifida, the Pia plant of the South Sea Islands. Portland arrowroot was formerly prepared on the isle of Portland from the tubers of the common Cuckoo Pint, Arum maculatum. Various other species of A rum yield valuable food-starches in hot countries. Under the name of British arrowroot the farina of potatoes is sometimes sold, and the French excel in the preparation of imi-tâtions of the more costly starches from this source. The chief use, however, of potato-farina as an edible starch is for adulterating other and more costly preparations. This falsification can readily be detected by microscopic examination, and the accompanying drawings exhibit the •appearance under the microscope of the principal starches we have described. Although these starches agree in chemical composition, their value as articles of diet varies considerably, owing to different degrees of digestibility and pleasantness of taste. Arrowroot is found frequently to remain in the stomach of invalids when most other forms of food are rejected, and on this account it has considerable therapeutic value. Being destitute of nitrogen, arrowroot and the other edible starches belong to the force-producing class of foods, and cannot of themselves form a perfect diet. They require to be associated with milk, eggs, meat, or other substances rich in nitrogenous compounds as articles of diet; and they should not be given to young infants, whose organs are not suited for the digestion of starchy food.