STEMS 117 



Conclusion. State the characteristics of the stem studied. 



(b) Method. As in Experiment 108 (6), make very thin 

 sections of dicotyl stems one, two, and three years old. 

 Mount them as before and study them with a low power. 



By moving the section slowly across the field of vision, 

 every region will come into view and can be observed in 



FIG. 43. Transverse section of a three-year-old twig of Pinus aylvestris, 

 showing the small pith, the thick and compact vascular cylinder of second- 

 ary wood, and the cortex ; radiating lines through the wood represent the 

 narrow pith rays ; resin ducts in both wood (small) and cortex (large) ; to 

 the right is a branch gap in the cylinder. 



detail. Compare bark with bast, cambium, and pith, making 

 note of the difference in size and shape of the cells and the 

 thickness of cell walls in the various tissues. 



