452 ELEMENTARY BIOLOGY. [CHAP. 



b. The roots springing from the rhizome. 



c. The leaves or fronds arising from the rhizome at 

 intervals, along the lateral lines. 



a. The great amount of subdivision of the frond : 

 its main axis (rachis); the primary divisions or 

 pinna ; the ultimate divisions or pinnules. 



/?. The sori ; small brown patches along the 

 margin of the under surface of some of the 

 pinnules. 



y. The indusium or membrane covering the 

 sorus. 



d. The nodes and internodes of the rhizome. The 

 naked growing point at its extremity. 



b. The rhizome. 



1. Cut it across and draw the section as seen with the 

 naked eye. 



a. The outer brownish layer (epidermis and hypo- 

 derma) ; the latter thins aways somewhat oppo- 

 site the lateral lines. 



b. The yellowish-white substance (ground-substance 

 or parenchyma) forming most of the thickness of 

 the section. 



c. The internal incomplete brown ring (sclerenchyma) 

 imbedded in the parenchyma. 



d. The small patches of sclerenchyma scattered 

 about in the parenchyma outside the main 

 sclerenchymatous ring. 



e. The yellowish tissue (vascular bundles or cylinders] 

 lying inside and outside the ring of scleren- 

 chyma. 



2. Cut a longitudinal section of the rhizome ; make out 

 on the cut surface b. i. a, b, c, d, e. 



