1 5 6 



THE STEM PROPER 



of dearth, to subsist for a while on the buds and bark 



of trees. 



221. Difference between 

 Dicotyledons and Monocoty- 

 ledons. Cut cross and 

 vertical sections of your 

 specimen, and sketch them 

 as seen under the lens, 

 labeling the different parts 

 that have been examined. 



300.-Secion across a young twig of Refer to Figures 3 OO and 



box elder, showing the four stem regions : 30 1 jf you have any diffi- 

 e, epidermis, represented bv the heavy , . j i_ ^u 



bounding line; ^cortex; w. vascular cylin- Culty in distinguishing the 



der; /. pith. (From COULTER'S " Plant parts . Notice the little 

 Relations.") . . , , 



pores or cavities that dot 



the woody part in the cross section ; where are they largest 

 and most abundant ? How are the rings marked off from 

 one another ? These pores are sections of the ducts already 

 alluded to (Sees. 214, 

 215). They are very 

 large in the grape vine, 

 and a cutting two or 

 three years old will show 

 them distinctly. Exam- 

 ine cross and vertical 

 sections of a twig that 

 has stood in red ink 

 from three to twelve 

 hours and observe the 

 course the fluid has 

 taken. (The rapidity 



771 



3oi. Section across a twig of box elder 

 three years old, showing three annual growth 



with which the liquid rings, in the vascular cylinder. The radiating 



IS absorbed varies with HneS ( w )- which cross the vascular region (a/), 

 represent the pith rays, the principal ones ex- 

 different Stems and at tending from the pith to the cortex (c). (From 



different seasons. It is ( 



most rapid in spring and slower in winter. In grape, 



plum, and peach it ascends quickly.) What should you 



