218 



POEOXYLEAE 



[CH. 



Fig. 464. Poroxylon. A, B, Poroxylon Boysseti. A, transverse section of leaf 

 in the region of lateral expansion of the petiole ; E, portion of vascular tissue 

 of A. C — E, Poroxylon Edwardsii. C, leaf -trace showing recent separation of 

 the two protoxylems ; D, leaf -trace at a lower level with more widely separated 

 protoxylems, px; B, leaf -trace intermediate between C and D. (From 

 photographs suppUed by Prof. Bertrand.) 



