CYCADOFILICALES 



13 



ugal tracheids of the metaxylem are sclariform and the centripetal 

 tracheids have multiseriate bordered pits. All the tracheids of the 

 secondary wood of the stele are pitted. 





I 



Fig. 7. — Lyginopteris oldhamia: p, primary wood; 5, secondary wood; /, leaf trace; 

 /, inner cortex; 0, outer cortex. The dark masses in the pith are groups of sclerotic cells. 

 The dark lines in the outer corte.x are radially arranged plates of thick-walled cells. — 

 From a photograph by Kidston. 



In most stems the cambium is poorly preserved, but occasional 

 specimens show it with the young secondary wood and phloem stand- 

 ing out almost as clearly as in a living plant (fig. 9) , 



