8 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



by Brown and Morris. It is not clear why the starch should 

 be less in the plucked insolated leaves than in those still 

 attached, and the large amount of maltose in the attached 

 leaves is equally hard to interpret. Perhaps it entered 

 through the petioles. No mention is made of the possible 

 passage of sugars from the petioles of the plucked leaves 

 into the water in which they were standing. This loss, 

 whatever its magnitude, would only go to increase still 

 further the differences between 6 and c. The altered con- 

 ditions of turgor in b as compared with a and c may have 



TABLE II. 



CARBOHYDRATES IN TROP^JOLUM LEAF. 



Total sugars per cent. 



9-79 17-18 



9-58 



some influence on the results, through a change in the con- 

 centration of the cell sap. This effect could, however, 

 hardly reverse the relative concentrations in b and c, for 

 b is more than twice as rich as c in sucrose. 



The great rise in the sugar content of 6 is due to the 

 sucrose and fructose, as the maltose has diminished and 

 the glucose remained almost constant. This the authors 

 regard as pointing to sucrose as the principal up-grade 

 sugar, rather than a hexose sugar as commonly believed 

 at the time. They explain the increase in fructose as due 



