XLV] SCHIZODENDRON 285 



petrified barrel-shaped piece of pith with portions of the inner 

 edge of the xylem-cylinder. The surface-features agree with those 

 of S. speciosum, each rhombic area being divided for a third of its 

 length by a median groove. The pith is composed of thin- walled 

 parenchyma with several secretory canals in the outer region; 

 patches of xylem are preserved in the depressions between the 

 lozenge-shaped areas showing the same anatomical characters as 

 those described by Potonie : internal to the secondary xylem are very 

 small groups of tracheids separated by 1 2 rows of parenchyma 

 from the secondary elements, which pursue a sinuous longitudinal 

 course. These tracheal strands are, as Weiss points out, at least 

 superficially comparable with the primary xylem of such a type as 

 Pitys antiqua. The innermost elements of the secondary xylem 

 are usually scalariform and these pass gradually into tracheids 

 with two alternate rows of bordered pits often slightly polygonal. 

 The leaf-traces are formed of two endarch strands which coalesce 

 as they pass downwards and eventually merge laterally with the 

 secondary xylem. 



Medullary casts with the external features of Schizodendron 

 might well belong to stems which are not identical in anatomical 

 characters, and from casts alone all that can be inferred is the 

 presence in the vascular cylinder of medullary rays with fairly 

 broad inner faces separated by prominent wedges of tracheids, 

 also the spiral disposition of leaves each supplied with a single 

 vascular bundle given off from the lower angle of the xylem- 

 meshes. In the case of Schizodendron Cowardi the presence of 

 small strands of primary xylem suggests comparison with such a 

 genus as Pitys or Mesopitys, while in the other examples there is 

 no indication of any xylem internal to the main cylinder. The 

 characters of the secondary xylem point to an Araucarian or 

 Cordaitean affinity and the pith agrees with that of Araucaria, 

 though in S. Cowardi the presence of secretory canals is a Cycadean 

 feature. Bain and Dawson 1 , though they did not correctly inter- 

 pret the surface-characters of Schizodendron, referred to it as 

 representing decorticated branches of the Conifer Walchia. Sterzel 

 recorded the association of Schizodendron with Walchia foliage- 

 shoots in Saxony, and Zeiller, who noticed a similar association 



1 Bain and Dawson (85). 



