THE CARBOHYDRATES OF THE ANGIOSPERM LEAF 13 



out even from hot solutions in characteristic clusters and 

 sheaves of yellow needles. The monosaccharides yield 

 these crystals in the cold, the disaccharide sucrose only 

 after inversion by prolonged heating of this acetic acid 

 reagent. Maltose, on the other hand, gives a phenylosazone 

 which crystallizes in very minute rosettes of needles, or 

 narrow plates, which are soluble in hot water. The reaction 

 with maltose necessitates heating on a water-bath for an 

 hour and a half. If a large excess of sodium acetate be added 

 to the solution it may be boiled without fear of inverting 

 the sucrose, and so the time required for obtaining the 

 glucosazone is greatly diminished. This affords a method 

 for the microchemical detection of sugars. Grafe (1905) 

 further enlarged the scope of this method by the intro- 

 duction of secondary asymmetrical methylphenylhydrazine 



C 6 H 5X 



/N NH 2 , which gives osazones only with ketonic 

 CH 3 



sugars after five hours at room temperature. For exami- 

 nation of microscopic sections of tissues the reagents may 

 conveniently be made up with glycerine instead of water, 

 as the sugars are less soluble in the former, and it does not 

 evaporate so readily. In this manner Mangham (1911) 

 proved the presence of maltose in sieve tubes of the bast of 

 certain angiosperms. [See also Mangham (1915).] 



THE DISTRIBUTION OF SUGARS AND SUCROCLASTIC 



ENZYMES IN THE BEET. 



Making use of the microchemical method just described, 

 Strakosch (1907) studied the distribution of sugars in the 

 sugar beet, Beta vulgaris. He found that glucose is con- 

 tained in the cells of the mesophyll, and that it is the only 

 sugar present. Diffusion of glucose into the veins is fol- 

 lowed by the appearance of fructose in them. Sucrose is 



