Contribution to the Study of Circulation. 



Studies on the Sweet Potato (Ipoma^a batatas.) 



B. H. A. GROTH, PH. D. 



The preliminary report on this investigation, pubHshed in the 

 Annual Report for 1909, recorded the progress of the experi- 

 ment from July 2nd until October 20th, 1909. A sweet potato 

 vine was planted in a box and its "Main Stem (M. S.)" and 

 "Main Branch (M. B.)" potted at regular intervals in pots 

 numbered i, 2, 3, etc. and A, B, C, etc., respectively. After 

 August 15th all water was withheld from the box and the pots 

 I, 2, A and B, and the effect of the partly reversed water current 

 upon the growth of the entire plant recorded. It was brought 

 out that the immediate effect was a sudden decrease in the rate 

 of growth on all parts of the plant, followed by a period of great 

 instability lasting for 39 days, and the establishment of an equi- 

 librium with a rate of growth lower than the original. (See 

 Ann. Rep. 1909, Plates XXVI and XXVII). 



On October 25th, 1909, after the plant had grown with a 

 partly reversed water current for 71 days, the plant was in the 

 following condition: The M. S. and its rosette (M. S. R.) had 

 practicahy stopped growth; all branches along the M. S. had 

 ceased to grow, and those between the box and pot 4 had dried 

 back to two internodes. The M. B. Rosette was growing at a 

 rate of 7.5 inches a day; all branches between the box and pot 3 

 had dried back to two internodes or less, with the exception 

 of the two branches S. B. i and S. B. 2 between the box and pot 

 A. These were growing at a steady rate of about 0.5 inch a 

 day. The curves for these rates of growth appear on the left 

 half of Plate XXVI. Some roots in the box had first slightly 

 decreased and then slightly increased in circumference. 



On October 25 all dry parts were again supplied with water, 

 like the rest of the plant. The curves on Plate XXVI show the 

 result as follows ; 



(283) 



