THE FUNCTIONS OF CHLOROPHYLL 239 



that several sugars occurred in leaves, and the relation- 

 ships of these to each other, to starch and to the activities 

 of chlorophyll, were problems that greatly exercised the 

 minds of chemists. Among the more recent contributions 

 to the subject are the papers by Parkin (191 1), who 

 claims the presence of glucose and fructose in the leaves 

 of the snowdrop, and of Davis, Daish, and Sawyer of 

 Rothamsted, who doubt the presence of maltose, as 

 asserted by Brown and Morris, but attempt to show that 

 pentoses occur, though Brown and Morris failed to identify 

 these sugars. With such contradictory statements before 

 us it is obvious that the last word on the precise carbo- 

 hydrates present in the photosynthetically active leaf 

 has yet to be spoken. 



Although Sachs had stated that starch was " the 

 first visible product " of photosynthesis, he also expressly 

 said that this did not exclude the formation of intermediate 

 bodies between that very complex product and the 

 primary water and carbon dioxide. That sugars were 

 to be included among such transitional substances was 

 apparent after Meyer had shown that some plants did 

 not form starch at all, and that some which did could 

 form it from a 10 per cent solution of fructose. Meyer, 

 Schimper, and others in the later years of the nineteenth 

 century proved conclusively that starch could be formed 

 from sugar both by chloroplasts and by colourless amylo- 

 plasts, and this strengthened the view, originally suggested 

 by Baeyer, that the primary product of photosynthesis 

 might be formaldehyde, whence a hexose might arise 

 by polymerisation, and which in turn might give origin 

 to sucrose or to starch. In 1907 Strakosch, during his 

 investigation of the sugars of the leaf, concluded that 

 glucose was the first sugar to appear and that sucrose 

 was an after-product. The rehability of the microchcmical 

 tests employed by Strakosch is, however, called in question 

 by Davis and his co-workers, and by Mangham in 1915, 

 for they point out that microchcmical tests arc of little 



