STRUCTURE OF THE FOLIAGE-LEAF 1 9 



The openings are stomata (Latin singular, stoma, a 

 mouth). The crescent-shaped cells are guard-cells. 

 How many has each stoma? 



4. Do the guard-cells and other epidermal cells contain 

 chlorophyll-bodies (chloroplasts) ? Describe their 

 shape. They are not considered identical with the 

 chlorophyll-band of Spirogyra, hence the different 

 name. 



5. Note the shape and arrangement of the other 

 epidermal cells. Are they in the same plane as 

 the guard-cells? Describe, giving reasons for 

 your answer. 



6. State the number of stomata visible in the entire 

 field (high power). Record three counts, each 

 of a different area, and the average. Why is this 

 desirable? After ascertaining the area of the ob- 

 jective of your microscope, calculate, from several 

 counts, the average number of stomata per square 

 centimeter. 



7. Make a drawing showing at least three stomata 

 with their guard-cells and adjacent epidermal cells. 

 The guard-cells should be at least 15 mm. long. 



THE UPPER EPIDERMIS 



8. As directed in B, 1-6 above, study the structure 

 of the upper epidermis of the same leaf. Draw. 



9. Compare the structure of the upper with that of 

 the lower epidermis, noting, among other features, 

 the relative number of stomata in each. 



10. In the light of the experiments on transpiration, 1 

 what do you think is one function of these stomata? 

 Of the guard-cells? 



1 This takes for granted that class demonstrations of transpiration have 

 been given. 



