190 



PRACTICAL BOTANY. 



outspread wings was the origin of the name Eagle Fern. 

 All above the lowest branches of the stipe is known as 

 the lamina or leaf. The leaf is pinnately and bipinnately 

 divided. Find, if possible, a fruiting frond. The spo- 

 rangia are borne around the margin of the under side of 

 the frond, protected by an indusium formed by the folding 

 over of the edge of the leaf. 



Draw a plant of Pteris, showing distinctly all its differ- 

 ent parts. 



2. Examine a longitudinal horizontal section of an apical 

 bud cut in the plane of the lateral ridges from a specimen 

 imbedded in celloidin. Find the apical 

 cell in the hollow at the end ; as seen 

 in section it is a triangle with rounded 

 base. (See Fig. 113, A.) This cell 

 divides by the splitting off of cells 

 first from one side, then from the 

 other side. These cells are known as 

 segmental cells ; they divide and sub- 

 divide to form new cells. Every cell 

 in the rhizome has originated through 

 the segmental cells from the apical 

 cell. It requires care and skill to se- 

 cure sections showing the apical cell. 



The cells which extend for a short 

 distance within and around the seg- 

 mental cell are thin walled and make 

 up an actively growing tissue known 

 as the apical meristem. As this tissue 

 continues to grow, its cells become differently differen- 

 tiated and develop into the various tissues of the rhizome. 

 Examine a vertical longitudinal section of an apical 

 bud. The apical cell, if included in the section, will be 

 seen to be polygonal in shape. (See Fig. 114, A.) This 

 section will serve well for a study of the different tissues 



FIG. 113. Horizontal 



longitudinal section 

 of the apical bud 

 of Pteris aquilina, 

 showing the apical 

 cell at A in process 

 of dividing. (X 480.) 



