340 The Dextrosc-Laccidose Ratio in t/ic Mangold 



associated with a sudden increase in the amoimt of a laevo-rotatory 

 impurity; at 4 j^.m. the hievulose curve rises above the dextrose curve 



and remains above it until 10 p.m. From G p.m. to 8 p.m. . has 



abnormally low values (0-749-0-789), but at 10 p.m. it is again practically 

 unity, and it so remains throughout the night with very little change, 

 although the laevulose curve rises and falls between 11 p.m. and I a.m., 

 and falls between 4 a.m. and 8 a.m. 



Day Night Day 



Fig. 2. Apparent dextrose and laevulose, Series II, Mangold leaves, Sept. 10-11, 1912. 



The curve showing the variation of the ratio y is also given in 



Fig. 2 ; it illustrates the marked periodic character of the fluctuations. 

 These occur in two well-defined periods : In the first, a regular rise 

 and fall of the ratio occurs in the eight hours from 10 a.m. to 6 p.m., 

 during which the dextrose appears in excess ; in the second period, from 



6 p.m. to 10 p.m., the laevulose is in excess, but the ratio — increasing. 



In the remaining 12 hours, from 10 p.m. to 10 a.m. there is Uttle change 



in the value y which remains very nearly unity. 



