142 



STEMS 



every form the color of the stem will show a decided variation 

 at different periods of its life history. 





FIG. 82.- Woody Stems. Upper figures are cross and longitudinal sections 

 of sassafras (Sassafras Sassafras). The middle figures are ailanthus (Ailan- 

 thus glandulosa). The lower figures are staghorn sumac (Rhus hirla). All 

 the figures at the left show the- central pith and annual rings. Staghorn 

 sumac shows the dark heart wood and light sap wood. The figures at the 

 right show the annual growth as parallel lines. 



