IX] EQUISETITES BEANI. 273 



received little attention at the hands of recent writers. In 1886 

 Starkie Gardner^ figured a specimen which was identified by 

 Williamson as an example of Bunbury's species ; but the latter 

 pointed out the greater resemblance, as regards the external 

 appearance of the Jurassic stem, to some of the recent arbor- 

 escent Gramineae^ than to the Equisetaceae. Williamson, with 

 his usual caution, adds that such appearances have very little 

 taxonomic value. Fig. 60 is reproduced from the block used 

 by Gardner in his memoir on Mesozoic Angiosperms ; he quotes 

 the specimen as possibly a Monocotyledonous stem. The fossil 

 is an imperfect cast of a stem showing two clearly marked 

 nodal regions, but no trace of leaf-sheaths. A recent exami- 

 nation of specimens in the museums of Whitby, Scarborough, 

 York and London has convinced me that the plant named by 

 Bunbury Calamites Beani is a large Equisetites. As a rule the 

 specimens do not show any indications of the leaf-sheaths, but 

 in a few cases the sheaths have left fairly distinct impressions. 



In the portion of stem shown in fig. 61 the impressions 

 of the leaf segments are clearly marked. This specimen affords 

 much better evidence of the Equisetaceous character of the 

 plant than those which are simply internal casts. The narrow 

 projecting lines extending upwards from the nodes in the 

 figured specimen probably represent the divisions between the 

 .several segments of each leaf-sheath. 



In the museums of Whitby and Scarborough there are some 

 long spt^cimens, in one case 44 cm. in length, and 33 cm. in 

 circumference, which are probably casts of the broad pith-cavity. 

 These oasts are often transversely broken across at the nodes, 

 so that they consist of three or four separate pieces which fit 

 together by clean-cut faces. This manner of occurrence is most 

 probably due to the existence of large and resistant nodal dia- 

 phragms which separated the sand-casts of adjacent internodes. 

 In the York museum there are some large diaphragms, 10 cm. 

 in diameter, preserved separately in a piece of rock containing 

 a cast of Equisetites Beani. The nodal diaphragms of some »)f 

 the Carboniferous Calamites were the seat of cork development', 



' Gardner (86) PI. ix. fig. 3. ' Williamson (88) p. 4. 



•'' Williamson and Scott (94) p. 889, PI. lxxix. fig. 19. 



18 



