rOBES IN Tin • -vrs OF PI.1NT5?. 31 



* 



aeCTlON III. CARBONIC ACID GAS OP THE ATMOSPHERE AB- 

 80RBEU AND DECOMPOSED BY THE LEAVES OF PLANTS. 



It has been said that this gas is necessary to the 

 life ol' the plant, and that the leaves draw it in from 

 the air. Those who have never studied the structure 

 of the leaf, will be surprised to hnd how admirably 

 it is adapted to this purpose. When examined by a 

 microscope, its whole surface is seen to be covered 

 with md beneath : each of 



thest , ii, intended to receive 



i(X)d, or to jjive olf something that the plant no longer 

 requires. These pores have an immense variety of 

 shapes and sizes in different leaves, as shown by the 



microt-cope. A ' • ' ■*•": power discovers more 



than 170,000 • inch upon the surface 



oi some leaves : uUit-rs txavc not ' .in 6 or 700. 



It is tasy for any person tosa;. -tlf that such 



pores do actually < : that the ditlerent sides of 



the same leaf hav< it properties. A common 



cabbage leaf, for instance, when applied with the under 



sidp to a wound or cut, will draw quite powerfully, 



I : i'..- a dLs«;harge, while the upper or smooth side 



Mce no such etftHt; thus sbowioff that on tlie 



are pon-s whii h have a power <M absorption. 



li iil)er and very small, it 



won llect enough carbonic 



hut we hnd that all plants which 



• ither quite large leaves, or a great 



Thus they are able to expose 



• 'o the passing wind, and to 



li i in the abape of earbonic 



it has been found that reiy 



. such as grape vines, melona, 



a, t'U., whin in full <: H as 



I > nearly all of the carlxM , ite a 



sMit current of air, so that only very slight traces of 



