34 SOME RECENT RESEARCHED IN PLANT PHYSIOLOGY 



vacuoles brought about by plasmolysis does not necessarily 

 lead to an increase in starch, and may even lead to its dis- 

 appearance. The regulation of the process appears rather 

 to be one of a very complicated nature depending upon the 

 amount of sugar and synthetic enzyme in the cytoplasm, 

 and upon the quantity of such enzyme secreted by the 

 latter under the influence of stimuli of which we are as yet 

 totally ignorant. 



The researches of Campbell on the mangold are being 

 continued and extended by Davis and Daish (1913 and 

 1914), who have as yet only published details of their pre- 

 liminary work on an exhaustive examination of the many 

 sources of error in such analyses."* 



SUMMARY or EVIDENCE AS TO THE FIRST SUGAR OF 

 PHOTOSYNTHESIS . 



It has been established that leaves supplied with glucose, 

 fructose, galactose, sucrose, maltose, or lactose, all form 

 starch, but those supplied with sucrose produce starch 

 somewhat more readily than do those which are placed in 

 solutions of the other sugars. Thus, unless the protoplasm 

 or enzymes bring about very rapid isomeric changes and 

 condensations resulting in the appearance of sucrose from 

 each of the other sugars, there is reason to believe that 

 starch may be built up from ma,ny different sugars. 



Maltose is universally regarded as a down-grade product, 

 arising from starch and giving rise to glucose. 



Of the hexoses, fructose and glucose, it appears that the 

 latter is more readily respired than is the former, and so in 

 the absence of any source of either the ratio of glucose to 

 fructose decreases. 



Sucrose on hydrolysis by invertase yields ^-fructose and 



* }Ir. Daish has since been wounded in Flanders. 



