io6 



Carbon Assimilation. 



assimilation." However, it is not clear how Brown and iVIorris's 

 work leads to this conclusion. The hexoses of the Z-series are not 

 fermented by yeasts and there is no evidence in Brown and Morris's 

 paper that these workers tested for hexoses of the ^series after the 

 rf-hexoses had been fermented away. Davis and Sawyer, on the 

 other hand, show that if this is done there still remain cupric- 

 reducing and optically active substances which they conclude are 

 pentoses, and they seem inclined to regard them as a mixture of 

 ^arabinose and Z-xylose, and they support this contention with 

 determinations of pentoses by the Krober-Tollens method in the way 

 we have already described, but without showing any great concord- 



Table XXVI II. 



Carbohydrates of the Leaf. 



E.xclusive of cellulose and pectin substances. 



