FEEN 331 



they contain ? In longitudinal section they ap- 

 pear as the scalariform tracheides already no- 

 ticed. Among the elements of the xylem look 

 for parenchymatous cells, the ■wood paren- 

 chyma. How do you recognize them ? "What 

 is their position ? What do they contain? How 

 do they differ from the bast parenchyma ? Draw 

 a fibro-vascular bundle as seen in cross and in 

 longitudinal section. 



Stain the sections with Schulze's solution, and 

 note carefully the color assumed by the various 

 elements of the bundle. 



Examine sections of the rachis made at points 

 where pinnae are given off and others made near 

 the upper end of the frond, and compare with 

 those from the lower portion. Note the differ- 

 ences in the sections and the changes due to 

 age. Study also sections made near the junction 

 of the rachis with the rhizome. 

 Draw the various structures observed in all of these 

 sections. 



2. The pinna. — Mount a piece of one of the pinnules 

 which bears no sori, and examine both surfaces 

 under the low power. What is the nature of 

 the surfaces? Are both alike? Of the mar- 

 gin ? Do you find any veins or fibro-vascular 

 bundles which are not visible to the naked 

 eye ? Does the green tissue, the mesophyll, 

 extend to the extreme margin of the pinnule ? 

 Cut horizontal sections parallel to the surface 

 on each side of the pinnule, thus removing the 

 epidermis, and examine with the high power. 

 What is the shape, as seen in surface view, of 

 the epidermal cells covering the mesophyll? 



