STUDIES OF THE FORMATION AND TRANSLOCA- 

 TION OF CARBOHYDRATES IN PLANTS. 



II. THE DEXTROSE-LAEVULOSE RATIO IN THE MANGOLD 



By WILLIAM A. DAVIS. 



(Rothamsfed Experimental Station.) 



Brown and Morris [1893] in their well-known experiments on the 

 TropcBolum leaf observed that the hexoses of the leaf instead of being 

 present in the proportion corresponding with invert sugar, invariably 

 appeared to consist very largely of laevulose. In several cases dextrose 

 was entirely absent, whilst in others the proportion of laevulose to dex- 

 trose varied from about 6 : 1 down to about 2:1. As they had concluded 

 on other grounds that the reducing sugars are formed by inversion 

 from cane sugar, they explained the predominance of laevulose as being 

 due to the dextrose being " more readily put under contribution for the 

 respiratory processes of the cell than is laevulose." 



Lindet (1900) made a special study of the proportion of the hexoses 

 present in the leaf and leaf-stalks of the sugar beet at different periods 

 of growth. His analyses showed that in normally growing leaves, 

 especially in the earUer stages of growth (July 3rd to 24th), the proportion 

 of dextrose was generally slightly (//'eate*' than that of laevulose, although 

 on several occasions it was shghtly less ; thus on July 3rd and July 24th, 

 for example, it was found that the ratio of laevulose to dextrose was 

 1-3 and 1-11 respectively. On the other hand and in striking contrast 

 to the leaves, the laevulose in the leaf-stalks was invariably found to 

 form only a small proportion of the dextrose present, varying from 

 to 35 per cent. Lindet adojjts Brown and Morris' views to explain 

 these results and concludes that the excess of laevulose in the leaves is 

 due to the dextrose being consumed in these tissues by respiration more 

 rapidly than the laevulose ; on the other hand the laevulose has been 



