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 lens of 

 the objective of your microscope, calculate, from sev- 

 eral 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. 



