EXERCISE 4 



WHAT HINDERS THE RAPID EVAPORATION OF WATER 

 AND COMPLETE DRYING OF THE LEAF? 



Materials. Leaves of lily, amaryllis, hyacinth, iris, or similar 

 plant; sharp knife. 



Directions for work. With the knife make a slight cut ob- 

 liquely through the surface layer of the leaf. Catch hold of the 

 surface layer at the edge of the cut with the thumb and the 

 knife blade, and peel off some of it. This is usually more 

 easily accomplished on the lower side of the leaf. The thin 

 layer removed is the epidermis. 



Remove the epidermis from as much as a half -inch or quarter- 

 inch square of leaf and allow a piece of leaf with epidermis 

 removed to lie on the desk alongside a piece with epidermis 

 uninjured for as long as an hour if possible. Note the changes 

 that take place in either piece. 



While waiting for the progress of the above experiment, 

 examine the epidermis carefully. Note especially its thickness, 

 color, and degree of transparency. Examine also the material 

 which occupies the interior of the leaf, noting its color, thick- 

 ness, and texture. Where does most of the moisture in the 

 leaf appear to be found? 



Compare the two pieces of leaf which have been exposed on 

 the desk as directed above. What changes have taken place ? 

 What are you able to conclude regarding the value of the 

 epidermis to the leaf? 



Write notes as in the preceding exercises. 



References 



BERGEN and CALDWELL. Practical Botany, pp. 13, 14. 

 BERGEN and CALDWELL. Introduction to Botany, pp. 34, 35. 



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