Jan. 7, 1918 Behavior of Sweet Potatoes in the Ground 1 5 



Moisture. — The moisture content of the roots remained almost 

 uniform during the period covered by the first three collections, from 

 September 18 to October 2. After that time there was a gradual increase 

 in the percentage of moisture until the end of the season. A small fluc- 

 tuation appears in the lot collected on November 6. The changes in 

 water content of the roots are therefore fairly regular and uniform. No 

 such marked fluctuations as those recorded in the tables of Keitt are 

 evident from these data. The beginning of the accumulation of moisture 

 in the roots is practically coincident with the destruction of the leaves. 



Starch. — The percentage of starch in the dry matter of the roots 

 shows a slight decrease from September 18 until October 23, varying 

 during that period between 71.39 per cent and 68.51 per cent. On 

 October 30, the date of the next collection, the starch content had fallen 

 to 64.65 per cent. From that date the starch content continued to fall 

 until the end of the season, when the minimum of 46.20 per cent was 

 reached. The rapid disappearance of starch follows, somewhat delayed, 

 upon the death of the leaves. 



Cane sugar. — The cane-sugar content remains practically constant 

 between 7.52 and 8.86 per cent until the time when the percentage of 

 starch begins to fall rapidly. With the decrease in starch the cane sugar 

 begins to increase correspondingly until it finally represents 26.06 per 

 cent of the dry matter of the roots. It should be noted, however, that 

 in general the changes in cane sugar are inaugurated somewhat later than 

 those of the starch. 



Reducing sugar. — ^The reducing sugar content remains constant at 

 first and then shows a gradual rise until the final percentage is somewhat 

 more than double that at the beginning. The increase in reducing sugar 

 antecedes somewhat the rise in cane sugar. It is noteworthy also that 

 under these conditions reducing sugar apparently does not accumulate 

 to the same extent to which it accumulates in sweet potatoes in storage. 



ToTAi, carbohydrates. — The total carbohydrate content undergoes 

 very little change until toward the end of the season, when the roots begin 

 to show marked injury by frost. At that time an evident loss of carbohy- 

 drates becomes apparent. The constancy of the total carbohydrate con- 

 tent of the sweet potato is in marked contrast to the fluctuations observed 

 by Keitt. 



The foregoing facts have been embodied in the curves in figure i. The 

 curves are based on the averages of the analyses for each week. 



CONCLUSIONS 



It may be concluded from this investigatiou that the changes occurring 

 in sweet potatoes in the ground during the later part of the growing 

 season proceed in a regular and orderly manner. During the later part 

 of the period of growth the composition of the roots remains remarkably 

 uniform, and presents no striking or irregular fluctuations. During this 



