CH. XXXVm] CYCADEAN STEMS 479 



of drawing a generic distinction between certain types of Cycadean 

 stems : in habit, in the form and structure of the leaf -bases, and 

 in the ramenta this species is identical with other species of Cyca- 

 deoidea, but it differs in the absence of lateral fertile shoots, a 

 feature that may have no morphological significance. It has 

 already been pointed out that the absence of flowers intercalated 

 among the leaf-bases may simply mean that the plant had not 

 reached the stage of flower-production, or their absence may be 

 due to some unfavourable conditions. Similarly the stems for 

 which Saporta proposed the generic name Clathropodium agree 

 in every respect with Cycadeoidea except in the absence, apparent 

 or real, of lateral flowering branches. Such types as Clathropodium 

 foratuin Sap. and C sarlatense Sap.^, the latter probably from 

 Upper Jurassic beds and the former from an unknown locality, 

 should be included in the genus Cycadeoidea. The stem referred 

 by Saporta to his genus Platylepis as P. micromyela^ was originally 

 assigned to Cycadeoidea and more recently Lignier has wisely 

 adopted the original generic name. The generic term Bolpopodium, 

 also instituted by Saporta^, is applied to small tuberous stems 

 which appear to be identical with the Cycadeoidea type. 



Having regard to the meagre data supplied by casts of stems 

 preserved in various stages of defoliation, and in view of the 

 impossibility of drawing other than purely arbitrary generic 

 distinctions, it is preferable to employ one generic name in a 

 liberal sense for stems that there is good reason to regard as 

 plants that cannot reasonably be referred to Cycadeoidea. The 

 name BucJclandia is thus employed, and a few examples are de- 

 scribed in illustration of the external features of stems that are 

 undoubtedly Cycadean but in most cases readily distinguished 

 from Cycadeoidea. There are substantial grounds for stating that 

 plants which bore flowers of the Williamsonia type possessed 

 stems having the characters of Bucklandia. It should, however, 

 be remembered that we cannot always draw a clearly defined 

 distinction between flowers included in Williamsonia and Bennet- 

 tites, or Cycadeoidea, particularly when they are represented only 

 by detached ovulate strobili as in Cycadeoidea (Bennettites) Morierei 

 and Williamsonia scotica. 

 1 Saporta (75) A. p. 293, Pis. 123, 124. ^ See p. 415. ' Saporta (75) A. p. 256. 



