LEAVES 



79 



the leaf. They open into very irregular and complicated spaces 

 between the mesophyll cells and permit free communication with 

 the air on the outside. These inner cells (mesophyll) take up 

 carbon dioxide, which is used in the making of carbohydrates 

 and give off oxygen and water in the form of vapor. The stomata 

 are also found on green stems and on green fruits but undergo a 



FIG. 61. Common forms of trichomes. 



special development into structures known as lenticels (Figs. 

 28, 29 and 30) (see page 52). In some plants certain ones of 

 the stomata are modified into structures known as water pores. 

 These water pores are enlarged stomata, which are formed at the 

 tips of the veins on the margins of the leaves of the fuchsia, cab- 

 bage, nasturtium and many other planta The water escapes 

 from them in much greater abundance than from the ordinary 

 stomata and frequently collects during the night in very notice- 

 able drops. The passage of water through these pores is known 



