CONTRIBUTION TO THE STUDY OF CIRCULATION. 



STUDIES ON THE SWEET POTATO (Ipomoea batatas). 



[Preliminary Report.] 



B. H. A. Gkotii, Ph.D. 



The nmning varieties of the sweet potato thrive in the sum- 

 mer heat of a greenhouse, grow very rapidly, and may be rooted 

 with ease at any joint, or as easily kept from rooting. They fur- 

 nish, therefore, excellent subjects for the study of the effects of 

 various treatments on the rate of gTOwth. This paper is a pre- 

 liminary report of an investigation of the ''Reversal of the Water 

 Current," caused by withholding water from the lower joints and 

 supplying it to the upper ones. 



On July 2d, 1909, a piece of vine of the variety "Big Stem 

 Jersey," which had one side branch, was planted in a lx)x in four 

 inches of soil, so that the two tips, one of the "Main Stem," the 

 other of the "Main Branch," protruded from the soil. The tem- 

 perature in the greenhouse ranged throughout July and August 

 from a minimum of 65-Y5° F. to a maximum of 95-105 every 

 bright day, and rarely fell below a minimum of 65 or below a 

 maximum of 90 on any day. The daily maximum gradually de- 

 creased in September to 80-90, and the minimum to ±60. On 

 October 15th the furnace was started, and since then the tem- 

 perature is maintained at ±70°. 



By August 15th the "Main Stem" had been rooted in six pots 

 (pots 1-6, Fig. 1) and the "Main Branch" in four. The "Main 

 Stem" had developed only small side branches, none of which 

 measured over six inches. The "Main Branch" had three large 

 branches, hereafter called "Side Branches 1, 2 and 3," between 

 the box and the first pot (pot A, Fig. 1), three others fairly long, 

 between pots A and B, and several small ones. Side Branch o 



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