376 



BENNETTITALES 



[CH. 



has more compact wood than that of recent Cycads ; the medullary 

 rays are 1 2 cells broad except near the perimedullary region 

 where they are broader and the individual cells are tangentially 

 stretched (fig. 508, B). The tracheids are scalariform, but in 

 C. micromyela, an exceptional type, some of the xylem-elements 

 have 1 2 rows of separate bordered pits (fig. 538). The phloem 



FIG. 509. Cycadeoidea Wielandi. Tangential section of secondary xylem of 

 the stem. (After Wieland; x 100.) 



(fig. 518, B) is characterised by an alternation of thick-walled 

 elements and thinner cells 1 . From the main stele branches are 

 given off to supply the flowering shoots in the form of a cylindrical 

 stele like that of the primary axis, and each leaf -trace arises as a 

 single bundle which, in the form of a U-shaped strand (fig. 519, A), 



1 Wieland (06) p. 76; Capellini and Solms-Laubach (92) PL v. fig. 6. 



