82 



CHLOROPHYLL 



rule rooted and immobile. As the prophet Isaiah said, "their 

 strength is to sit still." On the other hand, animals have to 

 seek for their food wherever they can find it. They have to 

 move about to seize it, and hence their bodies are compact. 

 They have to retain the food whilst it is being digested and 

 built up into protoplasm; therefore mth the exception of 

 certain parasites they have to have an "interior," a stomach 

 and an intestine. If they be carnivorous they have to develop 

 organs for killing and holding their prey. 



The actual feeding of the plant by the air is conducted as 

 follows. The atmosphere contains about 0-03 to 0-04 per 



,,'guard-cflf 



Fig. 9. Surface view of piece of lower epidermis of London Pride, showing 

 five stomata, and a section through a stoma, showing the guard-cells and pore, 

 and the large air-space immediately below the pore. 



cent, in volume of carbon dioxide. The percentage of carbon 

 dioxide in air is thought by some to be regulated not so much 

 by the amount given off from the green plant as by the 

 amount of the dissociation of the normal and acid carbonates 

 of the sea. The carbon dioxide finds its way into the tissues 

 of the leaf through the stomata or small pores which lead into 

 the intercellular spaces of a leaf, for a leaf is traversed by 

 small channels. In this way the carbon dioxide passes into 

 the chloropltyll-containing cells. At the same time water is 

 absorbed by the roots from the moist soil and passes up to the 

 leaves with the ascent of the sap. Then, omng to certain 

 wonderful powers that it possesses, chloroph3^11 is able by 

 the energy which it obtains from the sunlight to build up the 



