CHAPTER XXXII. 



CYCADOFILICES. 



IN this chapter are included several types represented by 

 stems, but which in the absence of definite information with 

 regard to the reproductive organs cannot be assigned to the 

 Pteridosperms. 



MEGALOXYLEAE. 



Megaloxylon. Seward. 



This genus is represented by a single species founded on a 

 piece of stem from the Lower Coal Measures of Lancashire 

 discovered in the Binney Collection in the Sedgwick Museum, 

 Cambridge 1 . Nothing is known as to the leaves, reproductive 

 organs, or roots. The type-specimen consists exclusively of 

 primary and secondary xylem. 



Megaloxylon Scotti Seward. 



The type-specimen, reproduced natural size in fig. 446, A, B, 

 consists of a fragment of stem which at first sight bears a close 

 resemblance to Cordaites, but the apparent pith, 1-9 cm. in 

 diameter, is the primary xylem of the stele and is enclosed by 

 an incomplete cylinder of secondary xylem 2 cm. broad. The 

 distinction between the lighter primary xylem and the darker 

 secondary cylinder is especially well marked in the longitudinal 

 section (fig. 446, B). The central region, shown on a larger scale 

 in fig. 447, is occupied by groups of tracheids varying in size and 

 shape associated with thin- walled parenchyma: the latter is 

 represented by lighter patches in the section. The majority of 

 the tracheids are characterised by their great breadth in some 



1 Seward (99) B. 



