THE INFLUENCE OF PLANTS IN EOOMS. 221 
How is its supply of carbon obtained by 
vegetation P 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. 
