PIN US SYLVESTRIS. 157 



20. The guard cells of the stomata also may usually be 

 seen. Draw. 



Cut a transverse section of the base of a young leaf, col- 

 lected at flowering time. 



21. Compare with the transverse section of an older leaf. 



Note the presence of protoplasm in almost all the 

 tissues, completely filling the cells. Clear with potash. 

 Compare carefully each tissue with the mature form, 

 noticing particularly the lack of differentiation of the 

 tissues, especially in the fibre-vascular region. 



Mount one of the scales which enwrap a young 

 leaf. Examine with a low power, and note 



22. The shape and arrangement of the cells. 



23. The fringe at the free end of the scale. Notice of 

 what each hair of the fringe consists. 



Cut a transverse section of these scales by cutting a 

 transverse section at the base of a pair of young leaves. 

 The sections of the scales will float off when the leaf section 

 is placed in water. Note 



24. The number of cell rows i-n thickness ; the shape of 

 the cells and thickness of the walls of some of them. 



25. A trace of a fibro-vascular bundle in the center of some 

 of the thicker scales. 



C. THE FLOWERS. 



i. The stamens. Tease out a portion of the wall of an 

 empty pollen sac. Examine with a high power, and 

 note 



a. The shape of the cells. 



b. The beaded appearance of the walls. 



