134 



PLANT LIFE. 



Hairs o£ many sorts, plain, stinging and glandular, and 

 of various sizes, arise from the epidermis (figs. 361-365). 

 They are essentially like similar structures on the stem (figs. 

 113, 114). 



166. Stomata. — Numerous intercellular spaces bounded 

 by a pair of specialized cells, called guard cells, penetrate 



Fig. 160. 



Fig. 162. 



Fig. 160.— Surface view of epidermis from the leaf of oat, showing elongated cells (more 

 elongated over vein, n, n) and stomata arranged in lines. Moderately magnified.— 

 After Frank. 



Fig. 161.— Perspective view of a stoma from the under epidermis of the beet leaf, show- 

 ing the sloping sides of the slit, the crescent'c guard cells with chloroplasts. Highly 

 magnified. — After Frank. 



Fig. 162.— Sections through stomata of beet at right angles to their length. The upper 

 figure shows the stoma open ; the lower closed. The black line represents the primary 

 wall, to which additional material, especially in the guard cells, has been added. 

 These thickenings serve by their elasticity to close the stoma. Opening is due to 

 turgor of the guard cells. The chloroplasts and granular protoplasm are shown. 

 Highly magnified. — After Frank. 



the epidermis. The whole apparatus is called a stoma (sf, 

 fig. 159, 160). The guard cells are crescentic, sometimes 

 with enlarged ends (fig. 160, like curved dumb-bells then), 



