THE SIGNIFICANCE OF CHLOEOPHYLL 23 



ment chlorophyll in transforming the radiant energy of 

 light into chemical energy, and this energy enables them 

 to form organic compounds from mineral matter. What 

 has been said about starch formation is not to be re- 

 garded as a statement of all that is involved in the 

 business ; it is a rough outline of a complicated piece of 

 chemistry. The chlorophyll may be extracted from a 

 leaf by soaking it in alcohol. The alcoholic solution 

 appears bright green when we look through it, but it is 

 fluorescent, and when we see it in reflected light, it 

 appears blood-red. After we have extracted the chloro- 

 phyll, we can demonstrate the presence of starch in the 

 chloroplasts by treatment with tincture of iodine; this 

 reagent turns the starch blue. We see, then, that sun- 

 light is necessary for the formation of chlorophyll, and 

 also in carbon assimilation, and, moreover, that the pig- 

 ment formed in sunlight is used by the chloroplasts in 

 transforming radiant energy into chemical energy. The 

 appearing of protoplasm was epochal in the history of 

 the world, and, we may safely aver, the development of 

 chlorophyll was an advance fraught with almost as 

 mighty issues. Green plants are of the utmost im- 

 portance as carbon assimilators and manufacturers of 

 organic compounds; they constitute the fundamental 

 food-supply: we could not exist without them, and they 

 could not do their beneficent work in the absence of 

 leaf-green. We take off our hats to chlorophyll ! - 



The reader wiU have already gathered from what has 

 been written that there are plants which do not possess 

 chlorophyll, and it will be obvious that they must 

 secure carbon compounds differently from green plants. 

 Among such plants are the Fungi, which, either as 



