DESCRIPTION.--The potato, a plant of the order _Solanaceae_, is supposed to be indigenous to South America. Probably it was introduced into Europe by the Spaniards early in the sixteenth century, but cultivated only as a curiosity. To Sir Walter Raleigh, however, is usually given the credit of its introduction as a food, he having imported it from Virginia to Ireland in 1586, where its valuable nutritive qualities were first appreciated. The potato has so long constituted the staple article of diet in Ireland, that it has come to be commonly, though incorrectly, known as the Irish potato. The edible portion of the plant is the tuber, a thick, fleshy mass or enlarged portion of an underground stem, having upon its surface a number of little buds, or "eyes," each capable of independent growth. The tuber is made up of little cells filled with starch granules, surrounded and permeated with a watery fluid containing a small percentage of the albuminous or nitrogenous elements. In cooking, heat coagulates the albumen within and between the cells, while the starch granules absorb the watery portion, swell, and distend the cells. The cohesion between these is also destroyed, and they easily separate. When these changes are complete, the potato becomes a loose, farinaceous mass, or "mealy." When, however, the liquid portion is not wholly absorbed, and the cells are but imperfectly separated, the potato appears waxen, watery, or soggy. In a mealy state the potato is easily digested; but when waxy or water-soaked, it is exceedingly trying to the digestive powers. It is obvious, then, that the great _desideratum_ in cooking the potato, is to promote the expansion and separation of its cells; in other words, to render it mealy. Young potatoes are always waxy, and consequently less wholesome than ripe ones. Potatoes which have been frozen and allowed to thaw quickly are much sweeter and more watery, because in thawing the starch changes into sugar. Frozen potatoes should be thawed in cold water and cooked at once, or kept frozen until ready for use.