FIELD CROPS. 755 



The potat(i tuber contains approximately 16 per cent of starch and only 0.4 per 

 cent of nitrogen. It is capable of retaining until spring 80 per cent of the moisture 

 contained at the time of harvest. During winter storage respiration is active and 

 water, carbon dioxid, and ammonia are given off. Chloroform vapor arrests the 

 exhalation of carbon dioxid and when the tuber is exposed to it for a prolonged 

 period the vital functions cease and a nitrogenous liquid exudes. When immersed in 

 carl)onic acid the tuber is asphyxiated and the solanin occurring principally in the 

 cells, which have changed to a green color under action of light, is o])tained. A low 

 tem})erature decreases the respiration of the tuber and causes an accumulation of 

 reducing sugar in its tissues. Freezing and subsequent thawing give rise to an exu- 

 dation of an acid licpiid containing solanin. In the tissues of the tuber ammoniacal 

 salts are found, and the author demonstrated that nitric acid disappears when a 

 solution of the salts is introduced into the parenchyma. The organic nitrogen of the 

 potato exists partially in the form of a compound insoluble in water, and the other 

 part, which is soluble, consists principally of albumin, coagulable at 70° C. After the 

 albumin has been separated b}' this process the solanin is found in the remaining 

 liquid. 



In the sjiring the potato produces sprouts spontaneously, but water must reach its 

 exterior to induce root growth at the base of these sjirouts. The author observed 

 that during gei'inination large starch grains of the tuber are in process of breaking 

 up and that small starch grains, ])re9umably derived from the larger <mes, are pres- 

 ent in the sprouts. Green sprouts growing in water containing starch used this sub- 

 stance fi)r food. The roots of sprouts took up ammonia, nitrates, and humic acid, 

 causing an increase in the nitrogen content of the plant. All parts of the plant 

 underground were found to contain nitrates. 



Sprouts separated from the tuber were successfully grown in nutrient solutions an<I 

 in rich soil kept moist with solutions containing plant food. The percentage of 

 organic nitrogen in the dry matter of the young plants doubled in several weeks. 

 The roots living in solutions took up nitric nitrogen until its supply was exhausted 

 and then utilized the nitrogen present in ammoniacal form. The sprouts separated 

 from the tuber and placed in rich soil accumulated large quantities of organic nitro- 

 gen and contained, after 5 months of growth, 460 times the quantity contained at 

 planting time. The author calls attention to the fact that a crop of 40,000 kg. of 

 potatoes per hectare, grown by A. Girard, took from the soil only 120 kg. of nitro- 

 gen, but concludes that the quantity contained in the stems, leaves, and roots of the 

 plants must havel)een considerably larger. 



Potash and phosphoric acid in the leaf ash of potato varieties rich in 

 starch, J. Seissl and E. Gross {Ztachr. Landw. Versuclifnv. Oesterr., 5 [190^), No. 6, 

 pp. iSt;2-875). — The results of fertilizer experiments made in this connection showed 

 that potash on the soils under test increased the yield of tubers and their starch 

 content. The use of phosphoric acid alone affected the quantity and quality of the 

 crop unfavorably. When the 2 elements were applied together, the detrimental 

 effects of the phosphoric acid were decreased but not eliminated. The use of potash 

 and phosphoric acid, alone or in combination, always increased the quantity of leaves 

 and stems. Where phosphoric acid was applied, the foliage was of an abnormal color. 



Ash determinations indicate that the content of potash and phosjihoric acid was 

 greater in the ash of leaves of varieties rich in starch than of varieties poor in that 

 substance. This relation existed during tlie entire vegetative period and was not 

 influenced Vjy the application of fertilizers. The use of phosijhoric acid as a fertilizer 

 in most cases increased the content of this element in the ash of the leaves, while the 

 application of potash liad the opposite effect with reference to itself. 



Variety tests with potatoes, E. S. Brown {Amer. Garcl., 24 [1903), No. 424, j)p. 

 86, 87). — A number of early and late varieties, some of which are new, w^ere tested 

 and the results are here reported, together with a brief description of the different 

 varieties under experiment. 



