PLATE XX. 



Fig. 168. 



Thready-bark Oak (Casuarina). 



Radial section showing the penetration 



of the Rays into the Bark. 



Fig. 169. 

 Bark of Thready-bark Oak seen from 

 without. The oval bodies are the ends 

 of the Rays. 



Fig. 170. 



Bird's-eye Maple. 

 Radial section through the worm-eaten 

 Bark, showing the origin of the figure. 



(Compare Fig. 34.) 



Fig. 171. 



As Fig 170, but viewed from without. 



