23 2 SHEPHERD' S P URSE. 



1 6. Wood fibers, length and nature of walls. 



17. Pith parenchyma, character of walls. 



1 8. Draw the various tissues. 



C. THE LEAF. Make a transverse section of a radical 

 leaf at right angles to the midrib, examine with a high 

 power, and note 



1. The epidermis, consisting of one row of empty cells on 

 the upper and under surfaces of the leaf. Observe 



a. Sections of stomata. Draw. 



b. Hairs of various kinds. Draw. 



2. The mesophyll, consisting of 



a. An upper row of oblong cells with longer axis at 

 right angles to the plane of the \zzi, palisade paren- 

 chyma. 



b. A lower region of rounded loosely aggregated cells, 

 spongy parenchyma, with large and small intercel- 

 lular spaces, those in connection with the stomata 

 being especially large. 



3. The fibro-vascular system. In the section of the midrib 

 note 



a. The position of the phloem and xylem areas with 

 reference to the leaf surfaces. 8 



b. The tissues in each as compared with those of the 

 stem bundles. 



In sections of the veinlets note 



c. The tissues that persist. 



4. Draw a transverse section of the leaf, illustrating all 

 the observed facts. 



8 Note how these positions follow from the relative positions of xylem 

 find phloem in the stem, 



