ILLUSTRATION No. 11. 



a 



A small portion of tissue from the lower surface of the leaf of a date palm (Phoenix dactylifera) 



magnified 600 diameters, 

 (a) Stomata (mouths) through which the plant takes in from the atmosphere various gases 



necessary for the elaboration or digestion of its foods, and passes out its gaseous waste 



products and excess of water in the form of vapour. 

 (6) Guard cells cells which control the opening and closing of the stomata. 



(See, jxira. 4, paye 9. ) 



