286 NEW JERSEY AGRICULTURAL COLLEGE 



Leaves were then removed from some portions between rooted 

 nodes. (The defoliated parts are designated in the diagram by- 

 very thick lines.) As will be seen, in most cases all leaves were 

 removed while in others the leaves were left on some side branch 

 springing off between pots. Up to four successive portions 

 were thus defoliated on the same branch. After that, all pots 

 received the same care, except that prospective branches from 

 defoliated portions were nipped in the bud. 



On November 15 all pots were emptied, and the roots roughly 

 weighed to 10 grams. As the nodes were rooted at various 

 times, the amounts found under each are of course not compar- 

 able with each other ; but they are all comparable with the yields 

 of the nodes near which portions of the stem had been totally 

 or partially defoliated. The figures on Plate XXVII give the 

 total yield in grams found in each pot. 



It will be noted at once that no pot which had a piece of totally 

 defoliated vine distal to it, contained any roots; all pots having 

 some leafy branches distal to them contained some roots; those 

 pots having the largest amount of foliage distal to them contain- 

 ed the largest amount of roots, although most of them were 

 rooted latest of all. 



This shows that the storage starch in a sweet potato plant 

 with the nomial direction of the water current is intercepted in 

 its course by the first roots basal to the leaf from where is 

 starts, and does not go beyond it. 



The bearing of the results of these two experiments upon 

 practice in sweet potato cultivation is evident. They show us 

 that — first, any portion of a many rooted sweet potato plant may 

 draw water from the roots most favorably situated. The roots 

 so situated are those under the main plant, in the hill. So 

 whenever a drought occurs, the rooted branches at any distance, 

 will draw water from the main hill. Second, every rooted joint 

 of any branch intercepts all the starch brought from all the leaves 

 beyond it and allows none to pass to the main hill. Thus in dry 

 time a rooted branch may feed upon the main root, but in the 

 best growing time it does not help the crop of the main plant in 

 the least. 



The conclusion is of course, that it is necessary to prevent root- 

 ing of the branches to produce the largest crop in the main hill. 

 Very likely the total yield would be largest where all joints 

 are allowed to root, but most of these joints would then not 

 have time to produce marketable roots. Where there is a very 

 long growing season it might even prove profitable to allow some 

 of the earlier branches to root. 



