THE INFLUENCE OF PLANTS IN ROOMS. 



How is its supply of carbon obtained by 

 vegetation ? The unobservant man probably 

 looks upon a plant leaf as ' only a leaf ' a thin 

 and opaque, or semi-transparent, thing with two 

 sides or surfaces of uniform green a flat un- 

 interesting object. He does not reflect that this 

 tiny green leaf, as he sees it softly waving in the 

 summer breeze, and now and then assuming a 

 golden tinge as it falls under the influence of sun- 

 light, is not only a living but a breathing thing. 

 Yet such it is : and it has a marvellous and 

 beautiful system of pores, through which to per- 

 form its breathing functions. The epidermis, or 

 outer-skin, of a plant leaf is studded by vast 

 numbers of these breathing pores, or stomates, as 

 they are technically styled. Usually these sto- 

 mates consist of little oval orifices, each placed 

 between a couple of sausage-shaped, superficial 

 cells. They are mostly placed on the undersides 

 of leaves, and an idea may be formed of the 

 extent to which a plant is perforated by these 

 minute apertures, when it is stated that there are 

 not less than a hundred thousand stomates on 

 each leaf of some plants. 



205 



