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 a temperature which at times may fall below the frost point on the surface of the soil. The leaf of the potato, when it has once appeared above the surface of the soil, is very susceptible to the action of frost. If killed at an early stage it may grow again without replanting. The potato is a crop which the farmer may plant early in the spring. There are other varieties which are planted later, even in the middle of summer, and produce good results. The planting season may continue over a period of two or three months. During the growth of the crop by the cultivation of the soil the surface is kept in good tilth, the weeds and grass prevented from growing, and the soil gradually drawn up around the growing tubers with the hoe or plow in the form of ridges. This heaping up of the soil tends to promote the development of the tubers, affording them a loose and more abundant bedding and a greater supply of plant food.

The greatest enemies to which the potato crop is obnoxious are found in the various forms of the potato bug (Doryphora decemlineata), which feed upon their leaves. To prevent the ravages of these insects it becomes necessary to dust over the leaves of the growing plants some powerful insecticide which will destroy the life of the insects feeding upon them. The active ingredient of these insecticides is usually arsenic. Fortunately the growing tuber does not absorb, so far as known, even traces of arsenic, or at least not more than the merest trace, which may be used for insecticidal purposes. It is quite impossible in most localities to secure a crop of potatoes without such treatment. The alternative is a constant inspection of the growing plant and the removal and killing of the bugs as they appear, but this is only practicable over very small areas as its general application would increase the cost of the product beyond the reach of the average consumer.

Yield.—Potatoes are produced in every state and territory of the United States. The statistics for the year ended December 31, 1905, show that the total area devoted to potatoes in the United States is 2,996,757 acres. The largest area in any one State is found in New York, namely, 428,986 acres, and the smallest area, aside from Arizona, not reported, is found in New Mexico, namely, 1,470 acres. The yield of potatoes for the year is given as 260,741,294 bushels. The largest total yield was in New York, the average yield per acre for the country being 87 bushels. The largest yield per acre is reported from Maine, namely, 175 bushels, and the smallest from Louisiana and Texas, namely, 64 bushels per acre. The average price per bushel for the whole country at the farm is 61.7 cents, making the total value of the crop $160,821,080. The highest price per bushel was obtained in Florida, namely, $1.20, and the lowest price per bushel in Nebraska, namely, 37 cents. The weight of a bushel of potatoes is 60 pounds. As the average amount of fermentable matter in potatoes grown in the United States is 20 percent,