A GREEN LEAF 



61 



colour is due to the presence of numerous micro- 

 scopic green granules embedded in their other- 

 wise colourless protoplasm, in the same way that 

 our blood, which is really colourless, appears red 



\ 



Fig. 40. The mid-rib or central vein of the laurel leaf, showing 

 its structure 



owing to the minute red corpuscles with which it is 

 crowded. These green " chlorophyll-corpuscles " 

 may be said to perform the most important func- 

 tion of any organism in the history of life, as we 

 shall see later. 



Below these palisade cells comes a kind of 



