CHAPTER XXXVIIl. 



CYCADOPHYTA. 



I. Cycadean Stems other than Cycadeoidea. 



Most of the stems now under consideration are represented 

 by casts or impressions and afliord no information with, regard to 

 anatomical characters. They are in many cases more slender 

 and less tuberous than typical Cycadeoideas, and a few are 

 characterised by an irregular form of branching, as is shown in 

 some specimens of pith-casts from Wealden strata in Tilgate 

 Forest figured by Mantell^ and now in the British Museum. The 

 genus Wielandiella^ (fig. 566) is an altogether distinct type repre- 

 sented by flowers as well as vegetative organs. Several generic 

 names have been proposed for Cycadean stems agreeing with those 

 of many recent Cycads in the possession of an armour of persistent 

 leaf-bases, but distinguished from Cycadeoidea in the absence of 

 any fertile lateral shoots intercalated among the petiole-bases. 

 It is, however, impossible in most cases to give any satisfactory 

 definition by which these genera can be distinguished from one 

 another; the characters employed by Carruthers^, Saporta*, and 

 other authors are of comparatively little importance as trust- 

 worthy criteria and to a large extent are merely the expression 

 of different states of preservation or of differences in age. Atten- 

 tion has elsewhere been called to the absence of any clear dividing 

 line between stems referred to Bucklandia, Yatesia, Fittonia and 

 Cylindropodium. The species Cycadeoidea gigantea described on 

 a previous page affords an instructive example of the difficulty 



1 ManteU (27). " See page 463. 



3 Carruthers (70). ." Saporta (75) A. pp. 256 et seq. 



