1 86 FIELD OATS. 



cells of the external sheath having slightly oblique 

 end walls. 



b. The delicate walls and elongation of the conduct- 

 ing cells. 



c. The pitted vessels, large and small. 



d. The annular vessels. Notice the various positions 

 of the rings. Study their cut ends where the 

 razor has passed along a vessel. 



e. Draw a few cells of each tissue. 



Cut a thin slice from the surface of a stem, examine 

 with a high power, and note 



14. The epidermis. 



a. The cells above the hypoderma ; shape and ar- 

 rangement. 



b. The cells above the chlorophyll tissue, including 

 the stoma ; shape and arrangement. 



c. The numerous pits in the surface wall, and in the 

 side walls beneath. 



d. Draw. 



C. THE LEAF. Cut a transverse section, and examine 

 with a high power. Study 



i. The epidermis. Notice 



a. Its cuticularized outer wall with minutely uneven 

 free surface. 



b. Ite guard cells. Note 



i. The different appearance of these cells, 

 according as the section has passed through 

 the bodies or ends. 



ii. The small size and thick walls of the body, 

 the larger size and thinner walls of the ends. 



c. The modified epidermal cells adjoining the guard 

 cells. 



