UPWARD TRANSPORT OF ORGANIC MATTER 19 



ground. The upper ring was made at this point and the 

 lower ring 10 cm. from the ground. This tree, with a 

 check of similar size standing close by, was cut on May 27. 

 At this time the growth in length of the shoots was prac- 

 tically completed and there were no apparent differences 

 between the shoot growth on the two trees. Data are 

 presented in Table 2. 



This table shows a direct relation between the sugar 

 contents, as shown analytically, and the starch contents, 

 as indicated by the iodine tests. The relation holds not 

 only where extremes in starch contents are compared, but 

 also where there are four gradations in amounts of starch 

 as shown by the iodine tests, which were made previous 

 to, and independently of, the sugar determinations. 



In these few cases where analyses were made, though the 

 amounts above the upper rings were low, a distinct and 

 easily measurable quantity still remained. In both 

 instances the rings were so far from the tip that sufficient 

 food was available above the ring to allow for seemingly 

 normal growth of the shoots. 



If analyses had been made of stems which had been 

 double-ringed nearer to the apex, it is probable that there 

 would have been much greater differences between the 

 sugar contents above the upper and between the two rings. 



Although in these ringing experiments the evidence is 

 rather clear that there is a direct relation between starch 

 content and soluble carbohydrate content, it is recognized 

 that this relation does not always hold. Evidence is 

 available from many sources (Appleman, 1912; Hopkins, 

 1924; and others) showing that temperature influences 

 the starch-sugar equilibrium so that, in the potato, for 

 example, at temperatures close to 0°C., starch tends to 

 decrease and sugars increase. These same investigators 

 obtained indications that this change is reversible, the 

 sugar changing back to starch at intermediate tempera- 

 tures. I have found also that at higher temperatures 

 (25 to 35°C.) the sugar again tends to increase at the 

 expense of the starch. Jones et at. (1903) found indications 



