POTATO, a perennial herb (Solarium tu berosum) of the family Solanaces. It is a na tive of the Chilean and Peruvian Andes. Its tuberous roots send up weak stems which bear pinnate leaves and white or lilac flowers which in cultivation are rarely followed by fruits. When fruits are produced they are globular, yellow or purple, and about the size of a goose berry. The plant is extensively cultivated in temperate climates for its tubers, which are used as a staple food for man, and to a less extent for animals. It was in cultivation before the discovery of America, and was taken to Europe (probably to Spain from Peru) in the early part of the 16th century. It seems that Sir Francis Drake introduced it into England in 1586, though Sir Walter Raleigh is said to have brought it with him the year previous. Gerarde mentions it in his Herbal' in 1597 under the name Batatas Virginiana, but it seems to have been regarded somewhat as a curiosity until the latter part of the 18th century, although the Royal Society of London had recommended it in 1663 as a possible safeguard against famine among the Irish peasantry. Owing to the failure of grain crops in 1772 soon com menced to grow in popularity as a food-plant, but even as late as 1771 only two varieties, one white and one red, were listed. In 1900 it was no uncommon thing for agricultural experiment stations in the United States and Europe to test more than 150 varieties at one time. The crop is one of the most important in Germany, France, Ireland and the United States. In the last-named country the yield per acre averages less than 100 bushels (1917), but with proper attention to cultivation, etc., yields of 200 to 400 bushels are not unusual, and even 1,000 bushels have been obtained under the best conditions. By artificial methods 2,558 pounds of tubers have been grown from one pound of seed in one season; but this was in a competition for prizes. The crop in the United States for 1917 was 442,536,000 bushels. Besides being an important article of food the potato is largely used in the manufacture of starch, and in some countries for making alcohol, etc. For such purposes special varieties are generally grown; these are usually coarse and are little used for human food.
The culinary varieties have been found to contain about 78 per cent water, 18 per cent starch, 22 per cent protein, 1 per cent ash and 0.1 per cent fat. During storage these propor tions change, since the tubers shrink nearly two per cent a month as an average for seven months.
Since the potato is rich in starch and poor in protein it is valued chiefly as a carbohydrate food, the deficiency of protein being made up by eggs, meat, fish, beans, peas, etc., and that of fat being supplied by butter, fat, oat-meal, etc. During the process of cooking the cells are ruptured, the starch expanded and made amealy,p and great changes in flavor and palatability are produced, either by the dissipation of raw flavors, the development of new ones, or both. In the cooked state more than 90 per cent of the nutritive substances are considered assim ilable. Large quantities of potatoes are annually evaporated to supply the demand for provision ing expeditions, camps, cruises, etc. Saratoga chips° are thin slices of potato which have been fried in fats or oils and sprinkled with salt. The potato is cooked ,in perhaps a greater variety of ways than any other vegetable, but fundamentally the various processes are baking, boiling and frying, the first being the most economical when properly performed.
Methods of Propagation.— The potato is propagated almost wholly by means of its tubers, which are cut in many ways intended to in crease the amount of °seed.* Some growers plant the whole tuber, others half-tubers, and others °single-eye pieces.' Probably there is no one method which is best under all condi tions of soil, cultivation, etc., but it seems as if the half-tuber of medium-sized, well-formed specimens is in most general favor. Extra large and little potatoes are not favored. In the propagation of new varieties seed-balls are used, and after the variety is proved to he worthy it may be increased rapidly by means of cuttings made from the sprouts. These are rooted under glass in the same way as geranium cuttings, etc., and the rooted plants set in good soil when the weather has become settled. Some growers expose their °seed potatoes' to the sun for about 10 days before planting in order to hasten the growth. Dunng this period of ex posure small rosettes of sprouts appear at the eyes, and it is claimed that some of the starch is converted into sugar, with the result that when the tubers are planted they make a more rapid growth than under ordinary conditions. With certain varieties and upon certain soils the period of growth may be shortened to eight weeks or even less.