XV] LEPIDODENDRON 175 



It is unfortunately seldom possible to connect petrified 

 Lepidodendron cones with particular species of the genus based 

 on purely vegetative characters, but it is practically certain 

 that we are justified in recognising certain strobili described 

 by Williamson' from the Calciferous Sandstone series of Burnt- 

 island on the Firth of Forth as those of Lepidodendron Velt- 

 heimianum. Williamson believed that the cone which he 

 described belonged to the plant with shoots characterised by the 

 anatomical features of his species Lepidodendron brevifolium 

 (=L. Veltheimianum),SL conclusion which is confirmed by Kidstonl 

 The cone of L. Veltheimianum, which reached a diameter of 

 at least 1 cm. and a length of 4 cm., agrees in essentials with 

 other species of Lepidostrobus ; the axis has a single medullated 

 stele of the same general type as that of the vegetative shoots 

 of Lepidodendron fuliginosum and L. Harcourtii. The sporo- 

 phylls are described by Williamson as spirally disposed, and 

 Scott notices that in some specimens they are arranged in 

 alternate whorls ; as in recent Lycopods both forms of phyllo- 

 taxis may occur in the same species. The heterosporous nature 

 of this strobilus, to which Scott first applied the name Lepi- 

 dostrobus Veltheimianus, is clearly demonstrated by the two 

 longitudinal sections contributed by Mr Carruthers and figured 

 by Williamson in 1893^ 



Each sporophyll, attached almost at right angles to the 

 cone-axis, bears a radially elongated sporangium seated on the 

 median line of its upper face; its margins are laterally ex- 

 panded as a thin lamina ; from the middle of the lower face a 

 narrow keel extends downwards between two sporangia belong- 

 ing to a lower series. From the base of a sporangium a mass of 

 sterile tissue penetrates into the spore-producing region as in 

 the large sporangia of Isoetes (cf. fig. 191, H, a, and fig. 133, H). 

 The distal and free portion of the sporophylls is bent upwards 

 as a protecting bract. Some of the sporangia in the upper 

 part of the cone produced numerous microspores, while 8 — 16 



1 Williamson (72) PI. xliv. p. 294 : (93) (QB^J. 



2 Kidston (01) p. 60. See also Scott (00) p. 170, figs. 67, 68. 



3 Williamson (93), PI. viii. figs. 61, 52. See also figs. 67—69 given by 

 Scott (00). 



