12 Journal of Agricultural Research voi.xii.no. i 



EXPERIMENTAL WORK 



In the present investigation Big Stem sweet potatoes were used. They 

 were grown at Bell Station, Maryland, in a sandy field having a gentle 

 slope to the south. Lots of 15 to 20 kgm. were collected each week from 

 September 18 to November 27. The collections were always made in 

 the afternoon. The roots were thoroughly washed and stored in a 

 covered receptacle in the laboratory until the following day, when the 

 samples were prepared for analysis. In each case moisture, starch, cane 

 sugar, and reducing sugar were determined in duplicate in five potatoes 

 of the lot. 



At the time of the first digging, September 18, the potatoes were still 

 small, so that it was difficult to get roots large enough to furnish the 

 requisite samples for analysis. After two or three weeks there was an 

 abundance of large roots.. The vines remained green and in a healthy 

 state until the week of October 9. Heavy frosts during that week, 

 especially on October 15, killed the leaves but not the stems. By 

 November 7 the stems which remained green after the leaves had been 

 killed were slowly dying, and some of the potatoes showed small round 

 injured spots on the portions near the surface of the ground or projecting 

 above it. On November 21 many of the roots showed considerable 

 injury on the exposed ends, but sound potatoes were still abundant. At 

 the time of the last collection, on November 28, the roots were so ex- 

 tensively damaged that it was difficult to find enough sound ones for 

 analysis. After that date the experiment was discontinued. 



The results of the analyses are given in Table III. For purposes of 

 discussion the analytical data have been reduced to the basis of dry 

 matter in the roots. These results are given in the left-hand part of 

 the table. Since it may be desirable to have for reference a record of 

 the actual percentages of the different substances contained in the pota- 

 toes, the original analytical data based on the fresh weight of the roots 

 are given in the right-hand part of the table. 



