146 VEGETABLE PHYSIOLOGY 



CHAPTEE 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 



