ABSORPTION. 



89 



readily perceived on the epidermis of the lily, where they 

 are unusually large. The epidermis must be first carefully 

 removed from one of the leaves, and having been freed 

 from all its chlorojjhyl, or green matter, it must be placed 



Fig. 22. 



Epidermis of the wliito lily, stowing tlae stomata st, composed of two cells, 

 with an opeaing or slit between them. 



between two slips of glass, with a drop of water between 

 them, so as to give it the necessary degree of transparency. 

 Water ought always for this reason to be used, whenever 

 objects selected from the tissues of plants are examined 

 microscopically. The epidermis, thus prepared, will ex- 

 hibit these pores, and the nature and beauty of their 

 mechanism will be seen and appreciated. 



It must be evident to all practical men, from these facts, 

 that it is of some importance to keep the leaves of plants 

 free from all impurities, which are apt to accumulate on 

 their surface and thus choke up their porous openings. 

 During dry seasons, a supply of water to the leaves is of as 



8* 



