140 Mr Seward, Notes on the Binney Collection 



some Lepidodendroid stems as examples of Lepidodendron Har- 

 courtii 1 , but in 1887 2 he contributed a note to the Royal Society 

 in which a new specific name — L. fuliginosum — was proposed for 

 certain specimens previously referred to Witham's species. This 

 proposal was the result of an examination of sections prepared 

 from the type-specimen of L. Harcourtii in the York Museum, 

 which led Williamson to recognise some points of difference 

 between this species and the closely allied stems which he had 

 confused with the true L. Harcourtii. In describing the distin- 

 guishing features of the two plants, Williamson lays stress on "the 

 greater uniformity in the composition of the entire cortex, the 

 inner part of which is preserved," and "on the absence of the 

 duplex structure of the foliar bundles " as distinctive features of 

 the former species (L. fuliginosum). He goes on to say, " The 

 small size of the cells of the inner cortex, and the dense aspect 

 both of it and of the foliar bundles, give to the transverse sections 

 of this form so sooty an aspect contrasted with the luminous 

 semitransparency of the true Lepidodendron Harcourtii, that I 

 propose to recognise the former (i.e. the specimens originally 

 described incorrectly as L. Harcourtii) as Lepidodendron fuligino- 

 sum." In describing these two species of Lepidodendron, Solms- 

 Laubach 3 refers to the presence of a group of "bast-fibres" in 

 the leaf-traces of L. Harcourtii (these so-called fibres give the 

 duplex form to the bundle as described by Williamson), and to 

 the larger and sharper projections of the corrugated face of the 

 primary xylem of the stem (Corona of Bertrand) as distinguish- 

 ing features of L. Harcourtii. Another recognised characteristic 

 of Witham's species is the absence or late development of second- 

 ary xylem as compared with the comparatively early formation of 

 secondary tissues in L. fuliginosum. 



A leaf-trace, as seen in a transverse section of the stem, ap- 

 pears to consist of two small groups of dark brown elements, 

 frequently enclosed by a small oval area from which the more 

 delicate cells have disappeared before mineralisation of the tissues. 

 It has been customary to describe one of the groups as the xylem 

 of the leaf-trace, and the other as representing a strand of bast- 

 fibres. In 1891 Prof. Bertrand of Lille published a memoir on 

 Lepidodendron Harcourtii 4 , in which he describes the leaf- traces 

 as consisting of xylem tracheids accompanied by a strand of latici- 

 ferous tubes. The examination of the Binney sections and of 

 several other sections in the Williamson collection and elsewhere 

 has convinced me that the term bast-fibres cannot be correctly 



1 Williamson (81), Pis. xlix. — lii. 



2 Williamson (87). 



3 Solms-Laubach (91), p. 226. 



4 Bertrand (91), p. 119. 



