jan. is, 1921 Tubers, Skins, and Sprouts of Potatoes 625 



OBJECT OF PRESENT INVESTIGATION 



It was thought that some variation in the composition of sprouts of the 

 same or different varieties of tubers might be found. It was also believed 

 that the copper sprays used to control Phytophthora infestans, or late 

 blight of the potato, might influence the time of sprouting — that is, 

 increase or decrease the rest period compared with that of the unsprayed 

 tubers — or that these sprays might modify the composition of the sprouts 

 of the same varieties of tubers, just as copper sprays apparently influence 

 the composition of the tubers. An investigation, therefore, was under- 

 taken to determine, if possible, whether any of the changes just men- 

 tioned took place and to secure data on the chemical composition of 

 sprouts, skins, and tubers. 



EXPERIMENTAL WORK 



DESCRIPTION OF SAMPLES 



In the course of some tests on the influence of copper sprays on the 

 control of Phytophthora infestans, or late blight of the potato plant, and 

 on the yield of the tubers, several samples of Maine and Connecticut 

 tubers dug in September, 1918, were stored in the laboratory at Wash- 

 ington, D. C, from October, 19 18, until they were analyzed in the spring 

 of 1919. Samples of Rural New Yorker (No. 12), Green Mountain 

 (No. 15), and Irish Cobbler tubers (No. 9) from Maine, from selected hills 

 where the vines were vigorous and healthy, as well as Green Mountain 

 tubers (No. 3 and 6) from Connecticut, taken from portions of the plots 

 which stayed green the longest were used for these tests. All the tubers 

 were held in a dark closet at laboratory temperature (average 70 F.) 

 from October, 1918, until February, April, or June, 1919. This rela- 

 tively high temperature may have affected the composition of both 

 tubers and sprouts. Several sprouts developed on each tuber, those on 

 the Rural New Yorker appearing later than those on the Green Mountain 

 and Irish Cobbler tubers. The sprouts of the Rural New Yorker tubers 

 were short and thick, while those of the Green Mountain and Irish Cob- 

 bler tubers were comparatively long and branching. 



METHODS OF ANALYSIS 



At the time of analysis the sprouts were removed from the tubers and 

 sifted to free them from adhering dirt. The tubers were washed and 

 dried and then pared as thin as possible, a difficult matter because of 

 their soft condition. The weights of the moist skins, tubers, and sprouts 

 were taken separately. The tubers and the skins were then ground 

 separately in a meat grinder, and each sample was well mixed and placed 

 in a Mason jar with rubber and top. The sprouts were placed in a stop- 

 pered bottle. The analyses were begun as soon as possible. Solids, ash, 

 phosphorus, and nitrogen determination were made on the moist samples, 



