lo DISEASE IN PLANTS. 



Bokorny, Saposchnikoff, and others, it soon became 

 evident that nothing essential needed altering in 

 Sachs' view that starch is the first visible product of 

 carbon-dioxide assimilation, only it became clearer 

 that the starch-grains are built up by the proto- 

 plasm from glucose or some similar body, and 

 represent so man}^ packets of reserve materials 

 put by for the present because not required for 

 the immediate needs of the cell. 



Boussingault showed, about thirty years ago, 

 that assimilation soon stops in green leaves if cut 

 off from the plant, not because the leaves die, but 

 owing to some " maximum capacity " being 

 attained. Sachs had shown that the starch 

 passes down to other parts of the plant in 

 solution as glucose. 



Neither time nor space will permit me to go 

 into the enormous field of research and results 

 opened up by these and similar observations 

 made between 1860-70. It must suffice to say 

 that they led to the discovery and study of the 

 diastatic and other enzymes in the leaves and 

 other green parts of plants, and to a clearer 

 understanding of what was already known of them 

 in seeds, and this knowledge reacted at once on 

 our insight into the processes of transport of 

 reserve materials and constructive materials from 

 one part of the plant to another, matters which 

 will be referred to later on. 



It remains to explain Boussingault's difficulty 

 as regards the cessation of assimilation. Recent 

 researches confirm the view that at least three 



