THE STOMATA. 79 



has no visible pores, it absorbs the water with an avidity 

 which indicates the permeabihty of its surface. Are 

 these pores simply inorganic, and such as philosophers 

 admit to exist in all substances ? Are they infinitely 

 small glands, which in some cases secrete the oily, waxy, 

 or resinous substances, which cover certain surfaces? 

 Do they serve for the usual passage of gas and vapours, 

 or for that of fluids? All these questions remain un- 

 answered. 



