DIRECTIONS FOR STUDY 69 



by the fusion of several cells through the 



disappearance of their end walls. 

 (9) Smaller sieve-tubes, resembling those of 



the phloem. 

 (10) Thin-walled cells forming the wood-, or 



xylem-parenchyma . 

 (n) Since the tissues of the nbro-vascular 



bundles are arranged circularly about a 



common center, the bundle is called a 



concentric bundle. 



(12) Compare the various bundles and see if 

 they are all of similar structure. 



(13) Make a careful drawing showing the 

 structure of the bundle, including all points 

 mentioned under (g), (i)-(io). This draw- 

 ing should be at least 75 mm. in longest 

 diameter. 



2. The pinna. 



(a) Under the low power examine a small portion of 

 one of the pinnae or pinnules not bearing a 

 sorus, and note the presence or absence of 

 outgrowths. 



(b) Can you observe any veins too small to be seen 

 with the naked eye? If so, describe their re- 

 lation to each other. 



(c) Mount a small bit of the lower epidermis, and 

 describe (a) any outgrowths; (b) the stomata 

 and guard-cells, stating the number, shape, 

 and contents of the latter. Describe the rela- 

 tive number and distribution of the stomata. 



(d) Compare the stomata of the fern with those of 

 a seed-bearing plant. 



(e) Make drawings showing all features shown 

 under 2, (b)-(d). 



