vii.] THE BRACKEN FERN. 63 



b. The rhizome. 



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

 naked eye. 



a. The outer brownish layer (epidermis and sub- 

 epidermis] ; the latter thins away somewhat, 

 opposite 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) lying in- 

 side and outside the ring of sclerenchyma. 



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

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



3. Cut a thin transverse section of the rhizome, mount 

 in water and examine with i inch obj. 



a. The single layer of much thickened epidermic 

 cells. 



b. The small opaque angular contours of the sub- 

 epidermic cells (external sclerenchyma}. 



c. The large polyhedral more transparent paren- 

 chymatous cells. 



d. The small opaque angular contours of the cells 

 of the internal sclerenchyma. 



e. The great openings of the ducts and vessels in 

 the fibre-vascular bundles. 



Draw the section. 



