ABSORPTION AND TRANSPIRATION. 



193 



atmosphere through the thin walls of any cells where 



it is not prevented by the cuticle (p. 172). 



Now, if you take the 



epidermis of some 



common land plant, 



and examine it under 



the microscope, you 



will find dotted here 



and there upon most 



parts of it, especially 



upon the leaves, the 



little openings, which 



are called stomates or 



stomata. 1 * Here is a 



niH-ntv* nf rarf nf HIP Fi ' 1 7. Epidermis of leaf showing 



pictured part or tne stomata (highly magn ified). f f. Figs. 

 surface of a leaf, very 20, 21, p. 25. 



much magnified, which shows a few of them (Fig. 170) ; 

 but they are very numerous, and are found chiefly 

 on the under sides of leaves.f The stomate is 

 generally formed of two sausage or kidney-shaped 

 cells placed together with the hollowed (concave) 

 sides facing each other, and so having a little opening 

 between them as in Fig. 170. But the opening between 

 them varies according as the cells are more or less 

 swollen with sap ; and the stomate is also much 



* From the Greek " stoma" a mouth : plural "stomata" 



t Botanists have calculated that there are more than 100,000 stomata 

 upon an ordinary sized apple leaf, and more than half a million upon 

 a leaf of the common lilac. 



In water plants the stomates are usually wanting in parts under water, 

 and are upon the upper surfaces of floating leaves. There are no 

 stomates upon roots. 



14 



