WORK OF THE SHOOT 



IOI 



and notice that with the sudden back-rush of water the 

 air-spaces of the leaf have become filled with water. How 

 can it enter the leaf ? What force has been exerted to 

 bring about this striking result ? 



The living cells of a plant are tiny chemical manufactories, 

 and very elaborate indeed are some of the compounds 



Fig. 62. Suction of Air through a Leaf. 



made there. The raw materials are carried to them in 

 the water from the soil and in the air which enters the leaves 

 and other green parts. The latter are exposed to the 

 influence of sunlight, and this is one of the necessary 

 conditions for the formation of the green pigment, chloro- 

 phyll ; otherwise plants would, as a rule, be sickly in colour, 

 as they are when grown in the dark. The presence of this 

 pigment gives to a shoot the power of utilizing the energy 



