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of starch, and have other desirable characteristics—as, suitable shape, color, depth of eyes, etc.
Selection.-Hybridizing is of small value unless attended by careful selection and vigorous elimination of the poorer types. All potatoes tend to vary in cultivation, either to improve or degenerate. This variation is more marked in some plants than in others; hence, once a variety is established, the yield may be materially increased and the rapid deterioration of the variety prevented by selection of the best plants. Selection must be made in the field, not from the bin. The whole plant must be considered, not a single tuber. Goff' showed that by perpetuating the most productive and least productive plants of Snowflake potatoes the total yield of the most productive one for two years was 322 ounces, while that of the least productive was but 100 ounces, and, summarizing fourteen years' trials, the most productive plants yielded 180 per cent. more than the least productive. Bolley, at North Dakota, found that “equal weight pieces from small or large tubers of the same vine are of equal value, provided all are normally mature," ? confirmatory evidence that the whole plant is the unit of selection.
Growers may at least maintain the productivity of their stocks of potatoes by careful selection of the best plants when digging, careful storage of these tubers, and then using all of them for seed. These might be planted by themselves on a piece of good land, and selections made from them at the following harvest, the best plants being again retained for the nursery plat and the balance used as seed.
1(N. Y.) Geneva Report, 1887, p. 85. Wis. Report, 1899, p. 306. 2 N. D. Bul. 30, p. 243.
A. Girard,' one of the foremost potato growers of France, selects his potatoes every year from those hills whose foliage is especially luxuriant. He uses the variety Richter's Imperator, and prepares the soil to a depth of 12 to 16 inches, giving a liberal application of barn-yard manure and fertilizers, acid phosphate, sulphate of potash, and nitrate of soda. He selects, for planting, tubers weighing from 372 to 4 ounces. When he cannot get such, he recommends that tubers of 7 ounces in weight be cut in two, and tubers of 10% ounces into three pieces—always cutting in the direction of the greatest length. He insists on the rejection of all potatoes weighing more than 11 ounces. If the potatoes available for planting weigh less than 372 ounces he places in each hill several smaller tubers, enough to bring the total weight to about 4 ounces. He lays great stress on the distance between the plants; the rows are 24 inches apart and the tubers are planted 19 inches in the rows, these distances having been determined to be best by careful experiment. He advises early planting, as soon as danger from frost is past. The crop should be well worked and all potatoes kept covered, and the tops well sprayed with Bordeaux mixture, and the crop not dug until all of the tops have withered. Farmers in the co-operative experiments under his direction report yields of 400 to 700 bushels per acre as common, and even up to 1,353 bushels per acre with a starch content of 20 to 25 per cent. One farmer secured almost 10,000 pounds of starch per acre, probably one of the largest yields of carbohydrates ever obtained from an acre of land.
1 E. S. R., V., p. 117.