Jan. IS, 1915 Changes in Sweet Potatoes During Storage 333 



subtemperate plant and not capable of long withstanding temperatures 

 much below freezing, resemble in their general trend those of subter- 

 ranean organs of temperate plants. In the more strictly tropical sweet 

 potato (Iponioea batatas) carbohydrate transformations of a similar na- 

 ture have been observed. Thus, Harrington (1895) found that in stored 

 sweet potatoes there was an increase of the total amount of sugar up to 

 March 6, bej'ond which the experiments were not continued. Shiver 

 (1901), whose experiments were somewhat more extensive, found that 

 during the time of his experiments (up to April 17) there was a gradual 

 decrease of starch and an increase of cane sugar, while the invert sugar 

 showed but slight fluctuations. Neither of these writers described the 

 conditions under which the potatoes were stored nor attempted to de- 

 termine the effect of temperature on the metabolic changes. 



The storage of sweet potatoes is accompanied by considerable losses 

 as a result of decay which is not wholly preventable by any of the methods 

 of storage advocated at present. The decay is brought about by micro- 

 organisms which invade the tissues. In the matter of susceptibility 

 the internal changes in the roots must play an important part. These 

 changes are affected by changes in temperature and other conditions to 

 which the roots are subjected during storage. It is therefore a matter 

 of practical importance, as well as of theoretical interest, to study the 

 internal changes which take place in sweet-potato roots after har\-est 

 and during storage, and to determine the effect of external conditions 

 upon such changes. The work reported in this paper is a general study 

 of the carbohydrate metabolism of sweet potatoes stored at different 

 temperatures. 



PLAN OF THE EXPERIMENTS 



For the purpose of this work two varieties of sweet potatoes, the Jer- 

 sey Big Stem, representing the sugary type, and the Southern Queen, 

 representing the starchy type, were selected. The potatoes used in the 

 experiments were a part of the general crop grown by the Office of Horti- 

 cultural and Pomological Investigations during the summer of 191 1 in 

 a series of variety tests which had been continued for a number of years. 

 At the time of harvesting, a representative lot of about 15 bushels of 

 each of the two varieties was selected in the field and packed in slat 

 crates holding about a bushel each. These were placed with the rest 

 of the crop in the sweet-potato cellar of the Office of Horticultural and 

 Pomological Investigations, where all were subjected to the "sweating," 

 or curing, process. During the period of curing, the temperature of the 

 room was kept at approximately 27° C. for about 10 days, after which 

 it was allowed to drop to the regular storage temperature, ranging in 

 this case, except near the end of the season, between 11.7° and 16.7° C. 

 Nine crates of each variety were left in the cellar at the above-mentioned 



