562 STUDIES IN FOSSIL BOTANY 



considerable part of this diameter was made up of the 

 persistent leaf- bases, as shown in the figure. The 

 American species Cycadeoidea marylandica, represented 

 in Fig. 1 99, was of larger dimensions, and may serve as 

 a typical example of the external characters of the 

 family. The great feature in which these stems differ, 

 even in outward aspect, from those of any recent 

 Cycads, is the presence of numerous short lateral 

 branches, resembling large buds, which are wedged in 

 here and there between the bases of the leaves 

 (Figs. 199, 200, f). These lateral appendages are the 

 fructifications, one of which is shown in Fig. 200, A, in 

 longitudinal section, inserted by a short stalk on the 

 stem, and lying horizontally between the bases of the 

 leaves. It is probable that the position of the 

 fructifications was axillary ; in any case they were 

 lateral branches, and cannot have been terminal on the 

 main axis, thus differing in position from the cones 

 of living Cycads. Hence, the fertile stem of Bennettites 

 appears to have had a monopodial, and not, as in the 

 recent Order, a sympodial construction. 



The main features in the anatomy of the stem were 

 worked out by Carruthers, whose conclusions have 

 been confirmed by the work of later investigators. The 

 structure is shown with special clearness in Bennettites 

 Saxbyanus, a species from the Wealden beds of Brook 

 Point, in the Isle of Wight (see Fig. 201). The large 

 pith is surrounded by a ring of wood and bast, of no 

 great thickness, built up as in normal Gymnospermous 

 stems, of anastomosing vascular bundles with collateral 

 structure. The histological details of both wood and 

 bast (which have more recently been minutely studied 



