CHAPTER II. 



ASSIMILATION OF CARBON. 



Section A. Formation of Starch. Section B, Evolution 

 of Oxygen. Section C. Reactions of Chlorophyll. 

 Section D, Conditions of chlorophyll formation : Etio- 

 lation: sun and shade leaves. 



Section A. Formation of Starch. 



(24) Sachs' Iodine-method ' (lod-Probe). 



This is a macroscopic method well adapted for many 

 experiments. Almost any leaves will serve as material 

 for the demonstration of the method, but since in research 

 it is of importance to employ material which allows of rapid 

 work, the choice of plants is a point to be considered. 

 Submerged water-plants are useful, and among land 

 plants, Tropseolum and clover are especially valuable. 

 The leaves to be tested are to be boiled for about one 

 minute in water ^, when they should be flaccid and free 



1 Sachs' Arbeiten, in. p. 1. 



^ Sachs allows a longer period, viz. 10 minutes, he states also that 

 the addition of a few drops of strong KHO to the boiling water hastens 

 the process. 



D. A. 2 ' 



