TRANSPIRATION. 



17 



Fig. 13.— Wood of the Eastern Sycamore or Button-ball tree. 



Fig. IT.— Cross section through a Black Oak. Milford. Pa. The silver grain, 

 the rings of annual growth, and the dark heartwood and lighter sapwood are 

 visible, and the line between the rough corky outer bark and the thinner and 

 lighter-colored inner bark may be seen. 



