140 



AGRICULTURAL BOTANY 



will be found rows of regular-shaped cells somewhat 



closely packed together. 



This surface being transparent is fitted to transmit 



the sunlight. The cells on 

 the underside of the blade 

 are more irregular in shape 

 and much less closely com- 

 pacted. They do not fill 

 the entire space, there being 

 some cavities between the 

 cells, called intercellular 

 spaces. 



From some of the larger 

 intercellular spaces there are 

 openings through the epi- 



FIG. 6 5 . -Magnified section of an dermis to the outside air. 



Apple Leaf from its Upper to its These Openings, Or mouths, 



are called stomata (singular, 

 stoma). Around each stoma 

 are two liplike cells which have power to close the open- 

 ing. They are 

 called guard cells. 

 If the cells of 

 the leaf are ex- 

 amined with a still 

 higher power mi- 

 croscope, we shall 

 see in all but those 

 of the epidermis 

 some small bod- 

 ies that contain 

 green coloring matter. This matter is named chloro- 

 phyll, and is what gives the green color to the leaf. 



Lower Surface. 



/, intercellular spaces. 



FIG. 66. 



S '3 



Stomata of an Oak Leaf (magnified). 



In A the under epidermis has been removed to show sto- 

 matu, g; B, a section of a stoma showing intercellular 

 space, a; guard cell, g; and orifice of stoma, s. 



