4 Weiss, XenopJiyton radiadosuni (Hick). 



specimen, while in most Stiginarice we find this tissue 

 very defective, it follows that we must consider the pith 

 in this Stiginaria as of greater strength and persistence 

 than is usually the case. 

 2. TJie stele. 



The central vascular cylinder is of the normal 

 stigmarian type, as seen from Hick's description and 

 figures. Fig. 2 of the present paper also shows this 

 typical stigmarian arrangement of the tracheids. There 

 is no clear demarcation between primary and secondary 

 wood, but a gradual transition from the smaller tracheids 

 near the centre to the larger ones near the periphery. 

 Smaller rows of tracheids seem to force themselves in a 

 somewhat irregular manner between the larger ones. The 

 AA'hole arrangement points clearly to a purely centrifugal 

 development of the wood which is so characteristic of 

 Stiginaria. The wood is interrupted by larger primary 

 medullary rays, opposite which the vascular supply to the 

 rootlets is given off 



The origin of the vascular supply to the rootlets can 

 be made out in one of the tangential longitudinal sections, 

 and has the appearance typical of Stiginaria* though 

 not in so striking a manner as is usual in that fossil, 

 owing to the small amount of secondary thickening. 



Outside the secondary wood there are rows of smaller 

 thin-walled cells, which, by their shape and regular arrange- 

 ment, indicate that they are of a secondary nature, and 

 they probably include the generative layer, or cambium, 

 though it is impossible to distinguish the actual meriste- 

 matic layer. 



Beyond this secondary tissue we find a small-celled 

 primary tissue, which must be taken to be equivalent to 

 the phloem of recent plants. The cells are often filled 



*cp. Williamson ('87) Plate V., Ftos. 8 and 16. 



