268 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



It might naturally be assumed that the first detectable 

 products would be simple sugars, such as bioses and tnoses ; 

 such trioses have not been found. On the other hand there is 

 evidence that acids, such as glyoxylic acid, CHOCOgH, and 

 glycollic acid, CHgOHCOjH, do occur in the leaves of plants, 

 and the interesting suggestion has been made that in the 

 process of reduction of carbonic acid, groups such as CHO, 

 CH2OH, CO2H, CHOH, etc., are formed, from which various 

 combinations, acids, aldehydes and carbohydrates may be built 

 up. At the same time certain of these compounds might 

 combine with ammonia, produced, it may be, by reduction of 

 nitrates, to form amino acids, the first products of albimiin 

 synthesis. Still the fact remains that these intermediate 

 products are not at all readily identified, and the evidence as 

 to their presence is conflicting. 



The careful experiments of Brown and Morris, in their 

 research on the chemistry of f ohage leaves, already referred to, 

 reveal the somewhat surprising fact that, in the case, at any rate, 

 of the nasturtium leaves, which constituted the chief material 

 of their research, the first product of assimilation is cane sugar. 

 Their method of experiment was to take leaves which were 

 gathered early in the day, and dried at once after plucking, 

 and compare their sugar content with leaves which were left 

 exposed to the sun for some hours after gathering, with leaves 

 which were gathered later on in the day and immediately dried, 

 and with others placed in the dark for some hours after pluck- 

 ing. The dried leaves were extracted with ether, to remove 

 fat and chlorophyll, and a weighed portion of the residue then 

 extracted with alcohol to remove the sugars ; the alcohohc 

 extract was rendered sKghtly alkahne with ammonia, to 

 prevent inversion of the sugars by means of the vegetable 

 acids, small quantities of albuminous matter and of tannin 

 removed by lead acetate, and the mixture of sugars in the 

 clear extract thus obtained, carefully analysed by polarimetric 

 and copper reduction methods, in successive stages, viz. : 



