274 



PTERIDOPHYTA. 



[CH. 



and it may be that the frequent preservation of Equisetaceous 

 diaphragms in Triassic and Jurassic rocks is due to the protec- 

 tion afforded by a corky investment. 



The stem shown in fig. 62 appears to be a portion of a 

 shoot of E. Beani not far from its apical region. From the 

 lower nodes there extend clearly marked and regular lines or 

 slight grooves tapering gradually towards the next higher node; 

 these are no doubt the impressions of segments of leaf-sheaths. 

 The sheaths themselves have been detached and only their 

 impressions remain. The flattened bands at the node of the 

 stem in fig. 60, and shown also in fig. 61, mark the place of 

 attachment of the leaf-sheaths. On some of these nodal bands 

 one is able to recognise small scars which are most likely the 

 casts of outgoing leaf-trace bundles. 



Some of the internal casts of this species are marked by 

 numerous closely arranged longitudinal lines, which are probably 

 the impressions of the inner face of a central woody cylinder. 

 In the smaller specimen shown in fig. 62 we have the apical 



Fig. 62. Equisetites Beani (Bunb.). From a specimen in the Searborough 

 Museum. Very slightly reduced. 



portion of a shoot in which the uppermost internodes are in 

 an unexpanded condition. 



