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 1 (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 con- 

 sidered. Submerged water-plants are useful, and among 

 land plants Tropceolum and clover (Trifolium) are especially 

 valuable. The leaves to be tested are to be boiled for 

 about one minute in water *, when they should be flaccid 



1 Sachs' Arbeiten, m. p. 1. 



2 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. 



