152 SCOTCH PINE. 



Examine with a high power, and study 



5. The epidermal cells. Note 



a. The very thick walls, their cavities nearly or quite 

 obliterated. The outer layers of this thickening 

 are cuticularized. 



b. The cuticle, quite thick and dipping as a thin 

 wedge between the cells. 



c. The crack-like pits radiating from the cavity. 



d. The enlargement of the cell which forms the corner 

 of the leaf. 



e. The stomata. Study their structure carefully, 

 noting 



i. The peculiar shape of the epidermal cells 

 above the stoma, the outer wall, about as 

 thick as the adjacent cells of the epidermis, 

 prolonged upward to form a ridge overarch- 

 ing the outer chamber of the stoma. Observe 

 the cavity of these cells, much larger than 

 those of adjacent cells. At the bottom of the 

 outer chamber, 



ii. The guard cells, their shape and the thicken- 

 ing of their outer walls. 



iii. The large intercellular space beneath the 

 guard cells, the inner chamber of the stoma. 



6. The usually single, in places double or triple, row of 

 small cells underneath the epidermis, the hypoderma, 

 Note 



a. The shape, and the thickness of walls. 



b. Where the greatest number of cell-rows occurs. 



c. The well-defined middle lamella. 



d. That the hypoderma is interrupted at each stoma. 



7. Draw a stoma with a few of the adjacent epidermal 

 and hypodermal cells. 



