OF LOWER GREEXSAND PLANTS. 329 



successive rings of secondary wood, appears similar to Cyca- 

 deoidea, particularly to C. buzzardensis (p. 309), the resemblance 

 is not a true one, because in Cycadeoidea the successive zones 

 appear to be like those of the living Cycas circinalis, formed 

 of fresh cambiums, so that each vascular /one is complete with 

 a region of phloem outside each wood. In the new fossil, the 

 zones of tissue between the successive vertical cylinders of 

 wood are hori/ontal cylinders of wood. It is, also, too unlike 

 Bennettites vegetatively to be included in that genus without 

 the compelling evidence of the fructification, nothing of which 

 is known at present. The cortical tissues and leaf- bases, which 

 also might have afforded useful evidence, are unfortunately not 

 represented, but so far as the leaf-traces go they seem different 

 from Bennettites^ both in their mode of exit and their constituent 

 tissues. 



The perimedullary zone of wood in this new fossil, while to 

 some extent paralleled by the wood-elements adjacent to the 

 pith in Bennettites, is much more extensive and specialised a 

 feature than in Bennettites. The species described by Wieland 

 (1906) as Cycadeoidea Jenneyana, having wood "as extensive 

 and compact as that of Cordaites" seems to show something 

 in the way of annual rings or special zones in its wood, but 

 without the evidence from thin sections nothing of use in the 

 present comparison can be deduced from the specimen. 



The leaf-traces in the present fossil are placed so close to- 

 gether that, if one leaf-trace went to each leaf-base, the leaf- 

 bases must have been exceptionally small for this group. 

 Without some indication of what happened in the cortex, 

 however, it is not possible to discuss the point. 



Concerning the most noticeable feature of the new plant, the 

 alternating cylinders of wood, but little can be said. As no 

 similar phenomenon appears to have been discussed for recent 

 plants, it is not clear how much systematic or phylogenetic 

 importance, and how much physiological importance, is to be 

 attached to this anatomical peculiarity. Among the Cycads 

 which do have series of cambiums, the various rings of wood 

 bear no relation to seasonal growth, and an ancient trunk shows 

 a maximum of ten or a dozen wood-rings. It is also probable 

 that the phenomenon in the new fossil is not a seasonal one. 

 If the alternations of the wood-cylinders do not depend on the 



