74 PROTECTION FROM INJURIES AND LOSS OF WATER 



Does either tissue (cork or epidermis) seem to be more efficient 

 than the other? 



10. Study cross-sections of leaves of mullein, Russian olive, 

 Crotonopsis, or sections of other leaves having a dense coating 

 of hairs and scales. 



Make drawings to show how these trichomes (outgrowths 

 from the epidermis) can help in reducing illumination and 

 transpiration. 



11. Cut out a piece of the hollow stem of Equisetum, and, 

 beginning with the inner surface, scrape away the tissues down 

 to the silicious outer incrustation of the epidermis. Put this 

 preparation into a strong chromic acid solution to macerate 

 and separate the organic parts from the incrustation. Rinse 

 the preparation and at the same time brush it with a soft brush. 

 Mount the preparation in a drop of dilute glycerine and study 

 it with low and high powers. Note how complete is the incrust- 

 ation, and the details about the stomata. Make a drawing 

 to show these things. 



