A GREEN LEAF 



77 



coming polluted by having- poured into it enormous 

 volumes of carbon dioxide, or more familiarly 



Fig. 50. Section through the base of a leat^-stalic prior 

 to its fall, allowing how the bark cells separate 

 the tissues 



carbonic acid g-as. Laro-e manufacturino- works 

 may turn thirty tons or more of this impurity into 

 the atmosphere in the course of a single day, while 



