STOMATES 



271 



Stomate of ge- 

 ranium leaf, show- 

 ing the guard cells. 



414. Stomate of ivy, showing 

 compound guard cells. 



in water on a slide. Make sketches of the different kinds 

 of hairs. 



437. STOMATES. Stomates or breathing-pores are 

 small openings or pores in the epidermis 



of leaves and soft stems to allow the 

 passage of air and other gases and vapors. 

 They are placed near the large intercel- 

 lular spaces of the mesophyll. Fig. 413 413> 

 shows the usual structure. There are two 

 guard cells at the mouth of each stomate, 



which may in most cases open 

 or close the passage as the condi- 

 tions of the atmosphere may re- 

 quire. In Fig. 414 is shown a 

 case in which there are compound 

 guard cells, that of ivy. On the 

 margins of certain leaves, as of 

 fuchsia, impatiens, cabbage, are 

 modified stomates known as water -pores. 



438. Stomates are very numerous, as will be seen from 

 the numbers giving the pores to each square inch of leaf 

 surface : 



Lower surface. Upper surface. 



Peony 13,790 None 



Holly 63,600 " 



Lilac 160,000 " 



Mistletoe -'.,' 200 200 



Tradescantia 2,000 2,000 



Garden Flag 11,572 11,572 



The arrangement of stomates on the leaf differs with 

 each kind of plant. Figs. 415 and 416 show stomates on 

 two plants, and also the outlines of contiguous epidermal 

 cells. The guard cells contain chlorophyll. 



439. FALL OF THE LEAF. In most common deciduous 

 plants, when the season's work for the leaf is ended, the 

 nutritious matter is withdrawn into the stem, and a layer 



