A GLIMPSE OF THE LIFE OF CHLOROPHYLLOUS PLANTS. 89 
If light is prevented from having access to a portion of 
a leaf while it is growing, by covering it with lead paper, 
or tinfoil, there is no difficulty in showing that the portion 
kept in the dark contains neither chlorophyll nor starch. 
Although it is a daring statement to make, I am of 
opinion that we do not know what is the composition of 
chlorophyll, for an analysis of it, like that of enzymes, 
means its death, and we are not able to say whether the 
whole or part of the inactive or dead substance is chlorophyll 
or not. One important point has however been established, 
that whether iron enters into its composition or not, it is 
absolutely essential for the growth of chlorophyllous plants 
that iron be present in even minute quantities in the 
nutritive material received from the soil. 
