146 VEGETABLE PHYSIOLOGY 
CHAPTER X 
THE CHLOROPHYLL APPARATUS 
The food materials whose absorption we have now discussed 
are built up in the body of the plant into such substances 
as are capable of being assimilated by the protoplasm, and 
consequently of ministering to its nutrition. They undergo 
a striking series of changes before they are capable of sub- 
serving this purpose, and of becoming incorporated into 
the plant-body. The great object to be attained is the con- 
struction and growth of the living substance, which itself 
subsequently produces the more permanent material that 
we find stored in the shape of the masses of wood and bark 
and the other substances which an adult plant contains. 
The green plant contains a mechanism for the formation of 
organic substance from these simple organic materials, 
and it is to the activity of this mechanism that we owe 
almost the whole of the organic matter which is found in 
nature, whether exhibited by animal or by vegetable struc- 
tures. This mechanism is known by the name of the 
chlorophyll apparatus, and our attention must now be turned 
to its nature and its mode of working. 
Chlorophyll is a green colouring matter which is gene- 
rally found associated with definite protoplasmic bodies 
known as plastids. These are usually considered to possess a 
reticulated structure, and the pigment, in some form of solu- 
tion, occupies probably the meshes of the network. From 
their being coloured green by the pigment they are known 
as chloroplastids or chloroplasts. The solvent of the 
