44 CYCADEAN STEMS. 



any essential distinction between these stems and those of Cycadeoidea. 

 We cannot enter into a detailed consideration of the various other 

 generic terms applied to Cycadean stems, but mention may be 

 made of one recent addition by Lester "Ward. He has instituted 

 the genus Cycadella^ as a generic name for Cycadean stems especially 

 ■characterised by the abundance of the woolly or scaly ramenta 

 which formed a thick covering over the greater part of the surface 

 of the stem. It is, I think, doubtful whether this new term is 

 really needed ; the extent to which the ramenta may be developed 

 on the petioles and scale-leaves is hardly a character of generic 

 rank, but in all probability the peculiarity of the stems referred to 

 GycaAella is an expression of certain external conditions which led 

 to an unusual development of ramental scales. It is hopeless to 

 attempt the separation of Cycadean stems into distinct genera if 

 we take as our criteria such characters as the form of the leaf- 

 bases and their degree of prominence, the relative length of the 

 stem, and other characters of the same kind. The English trunks 

 referred by Carruthers to Presl's genus JBuoJclandia and to the 

 genus Yatesia are not distinguished by any striking or important 

 features, and the same criticism may be applied to other forms 

 referred to distinct genera. 



Among existing Cycads there are some, e.g. species of Zamia, 

 which possess stems covered by a corky investment which shows 

 no signs of persistent leaf-bases.^ It is probable that stems of this 

 type are also represented among fossil Cycads. 



The generic name Benstedtia' was suggested for some English 

 stems of Lower Greensand age in 1896, and I have more recently 

 made use of the same genus for certain South African stems 

 which are probably Cycadean. 



Leaving out of account such stems as there is reason for including 

 in the Cycads and which are without the covering of persistent 

 petiole-bases, it would make for less artificiality in our nomen- 

 clature if we grouped under the generic designation Cycadeoidea all 

 Cycadean trunks, whether bulbous or of the longer and narrower 

 form, which are covered with persistent leaf -bases, and which show 



"SYard (00), p. 392 ; (00-). 

 Se-\vard (96), pi. xiv. fig. 1. 

 Seward (96) ; (03), p. 34. 



