EQUISETITKS. 65 



which had been previously named by Bean, in unpublished notes, 

 Calamites giyanteus. Bunbury's species is referred to by Schimper 

 as being possibly founded on the pith-cast of Equisetites columnar is. 

 In 1886 Starkie Gardner published a figure of a specimen which 

 was identified by Williamson as an example of Calamites Beam', 

 and compared by the latter author with recent arborescent 

 Gramincse. Text-fig. 5 is taken from the block used by Gardner 

 in his paper on Mesozoic Angiosperms, in which the specimen is 

 quoted as possibly a Monocotyledonous stem. The cast shows two 

 conspicuous nodal regions, but no trace of leaf -sheaths, and affords no 

 definite evidence of its Equisetaccous nature. Casts like that figured 

 by Gardner occur in the Whitby, York, and Scarborough Museums, 

 and in some cases reach a length of over 40 cm. ; they have the 

 form of cylindrical or more or less compressed stems, divided by 

 transverse nodal constrictions into fairly long internodal regions, 

 and occasionally the easts of the several internodes occur as separate 

 pieces, fitting together by clean-cut faces. The larger specimen 

 represented in Text -fig. 6 shows not only nodal regions, but 

 distinct indications of leaf-sheaths which reveal the Equisetaceous 

 character of the casts. Some of the pith-casts of these steins exhibit 

 a fine longitudinal striation on the surface, which suggests the 

 presence of a woody cylinder enclosing the wide pith ; it is probable 

 that these large stems grew in thickness by the development 

 of secondary vascular tissue, but we have as yet no precise 

 information as to their anatomy. In the York Museum there 

 are some large circular discs 10cm. in diameter, enclosed in the 

 matrix of a rock containing a cast of Equisetites Beani, which 

 undoubtedly represent the nodal diaphragms of this species. 



V. 2725. Text-fig. 6. 1 



This large cast measures 27 cm. in length, and at the second 

 node from the bottom has a breadth of 1 2 cm. There are seven 

 nodes shown on the stem : the two lowest nodes exhibit 

 distinct impressions of numerous narrow segments of leaf-sheaths, 

 the impressions having the form of tapering narrow ridges 

 representing the grooves between the segments, as seen in 

 surface-view. It is possible that this form of stem may belong 



1 Figured also in Sewurd (98), p. 271, fig. 61. 



