2l6 



STUDIES IN FOSSIL BOTANY 



the convex side towards the pith. The small, spiral 

 tracheides are placed on the outer, slightly concave, 

 side of each bundle. The rest of the primary xylem- 

 elements, which are irregularly arranged, and increase 



Fig. 89. — Sigillaria Menardi (Clathraria type). Brongniart's original specimen, show- 

 ing transverse section and part of surface with leaf-scars, a, pith (perished) ; b, 

 primary wood, forming many distinct bundles ; c, secondary wood ; d, phloem- zone ; 

 e, middle cortex (perished) ; /, periderm ; g, leaf-base ; k, foliar bundle, x about 2. 

 After Brongniart. 



in size towards the interior, are reticulated or finely 

 scalariform tracheides. 



The secondary zone, which is almost continuous, 

 though showing some signs of division into distinct 

 bundles corresponding to the primary strands, consists 

 of radially arranged scalariform tracheides, and narrow 



