THE FLO WEEING PLANT STEMS 353 



ments show large openings. Note the appear- 

 ance of the annual rings. In the centre lies the 

 pith, or medulla. Make a diagram showing the 

 arrangement of all these parts. Put on the high 

 power and study the structure of each of these 

 tissues. Do you find an epidermis ? If so, does 

 it form a continuous layer ? What is the struct- 

 ure of its cells ? Contents ? How many cells in 

 thickness is the cork -layer? What is their 

 shape ? Are there any intercellular spaces ? Do 

 these cells have a definite arrangement ? Do the 

 walls of these cells vary in thickness ? Compare 

 the outer with the inner cork-cells. What do the 

 cork-cells contain ? Do you find any places where 

 a mass of cork-cells has pushed through the epi- 

 dermis and formed a lenticel ? What is the shape 

 of the cells of the cortical parenchyma? Com- 

 pare their arrangement with that of the cork- 

 cells. What contents have these parenchymatous 

 cells? Do you find any crystals? If so, test 

 them with acetic and hydrochloric acids. Of 

 what are the crystals composed? How are the 

 bast-fibres arranged? Is the ring of bast-fibres 

 broken or continuous? What is their shape? 

 Contents? How do you distinguish the soft 

 from the hard bast or bast fibres? Note the 

 arrangement of the cells of the cambium. Does 

 it form a complete ring? What is the shape of 

 its cells ? How do their walls compare in thick- 

 ness with those of the other cells in the section ? 

 Do you find that the cells of the tissues (xylem 

 and soft bast) on each side of the cambium have 

 the same arrangement as the cells of the latter ? 

 If so, explain. Note the arrangement of the ele- 

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