560 STUDIES IN FOSSIL BOTANY 



Carruthers in 1868, for several species, ranging from 

 the Middle Oolite to the Lower Greensand. The 

 characters of the genus were thus given by the author 

 in his classic memoir : — " Trunk ovoid, in transverse 

 section elliptical, covered with the somewhat long 

 permanent bases of the petioles. Medulla entirely- 

 cellular, with numerous gum-canals. Wood consisting 

 of a thin interrupted cylinder of striated tissue, every- 

 where penetrated by medullary rays. Fruits borne on 

 secondary axes, not protruding beyond the bases of the 

 petioles." 1 



The elliptical transverse section of the stem has not 

 proved to be valid as a generic or even a specific character, 

 but on the whole the short description just quoted still 

 holds good. The American palsobotanists use Buck- 

 land's generic name Cycadeoidea in preference to 

 Bennettites. 



The following account is based in the first instance 

 on the observations of Carruthers (who laid the 

 foundation of our knowledge of the group), Solms- 

 Laubach, Lignier, and others, confirmed, as regards the 

 fructification of Bennettites Gibsonianus, by a study of 

 the original preparations. The still more important 

 results obtained from the investigation of the American 

 material by Dr. Wieland have in some respects pro- 

 foundly modified our conception of the group, and will 

 be considered in due course. 



In external aspect, the stems of the Bennettiteae 

 presented the same general appearance as those of the 

 recent Cycads in which the stem remains clothed in an 



1 Carruthers, "On Fossil Cycadean Stems from the Secondary Rocks 

 of Britain," Trans. Linnean Soc. vol. xxvi. 1870. 



