20 TRANSLOCATION IN PLANTS 



of marked sugar increase in the maple at a temperature of 

 about 0°C. or below, and Sinnott (1918) also observed 

 indications of such a change. Neither, however, has 

 presented analytical data. Riissow (1884), Fischer (1891), 

 Sinnott (1918), and others have observed also a disappear- 

 ance of starch and an appearance of fat at low temperatures. 

 These changes have been observed only at rather extreme 

 temperatures. The temperature at the time that starch 

 tests were made on twigs reported in my first paper (1920a) 

 in no instance approached 0°C. but usually varied between 

 10 and 20°C. The maximum and minimum during the 

 24 hours previous to the determination for Acer in Table 2 

 was 17 and 7°C., respectively, and that for Fagus was 



21 and 16°C., respectively. Furthermore all parts of the 

 stem must have been exposed to the same temperature. 



The water supply also has been found to influence the 

 starch-sugar equilibrium. Lundegardh (1914), Bruns 

 (1925), and several others have observed that, when water 

 becomes deficient and leaves begin to wilt, starch may be 

 transformed into sugar. In the experiments on ringing, 

 however, water did not become deficient. There was very 

 little sunshine during the month the tests were made and 

 there had been rains amounting to over half an inch or 

 more during the week preceding the time each twig sample 

 was taken. Even if the water supply were a factor, there 

 is no evidence that the supply to the region between the 

 rings would be very different from that to the region above 

 or below. Starch tests on leaf tissues seem more likely to 

 be affected by water changes than in the stem tissues here 

 used. 



Light or hydrogen ion concentration may also influence 

 the sugar-starch equilibrium, but the different parts of the 

 stem received similar light exposures and I know of no 

 evidence that would indicate that hydrogen ion differences 

 might be concerned in the experiments reported. It has 

 been repeatedly demonstrated by many investigators 

 that starch removal or deposition is closely correlated with 

 sugar removal or accumulation in many different types of 



