240 PLANT ANATOMY. 
always a more or less wide respiratory eavity (Figs. 155 A, 179 
Fie. 156. Fie. 157, 
Fias. 156, 157, 158.—Stomata from dicotyledons and monocotyledons on a surface sec- 
tion, as seen from above. 
3  @); and occasionally, beside the guardian cells, peculiarly formed 
