80 GENERAL BIOLOGY. 



1. The tracheids. Why is a larger number of 



pits visible in this section ? 



2. The medullary rays. 



Make a diagram shoiving tlie relation of tracheids 



and medullary rays. 

 Sketch a few tracheids much enlarged. 



From what has been seen in the three sec- 

 tions describe the shape of a medullary 

 ray. 



II. Angiosperm. 

 A. Dicotyledon. 



Ampelopsis. Prepared transverse section of 

 entire, young stem. Study with AA 2 and D 2. 

 AA 2. Observe : 



1. Epidermis, one cell-row in thickness. 



2. Cork (subepidermis) consisting of several 



layers of flattened cells. 



3. Cortical parenchyma. 



4. Fibrovascular bundles. 



5. Pith. 



6. Medullary rays. 

 Diagram. 



Which tissues have cell-contents ? 



Cut a section from fresh material and see 



which tissues contain chlorophyll. 

 D 2. In the fibrovascular bundle observe the 



cambium layer dividing the bundle into 



an inner part (xylem) and an outer part 



(phloem). 



