BOTHRODENDRON 201 



exterrtal features of a Bothrodendron has the anatomical 

 structure of the Lepidodendron mundum of Williamson. 1 

 The structure of Bothrodendron mundum, as the species 

 may now be provisionally named, is of a simple 

 Lepidodendroid type. In the larger stems there 'is a 

 massive pith, surrounded by a comparatively thin zone 

 of centripetal wood with well-marked protoxylem 

 groups ; in the more minute twigs, however, the xylem 

 is solid. A characteristic feature is the radial arrange- 

 ment of the primary tissue of the outer cortex, quite 

 apart from the subsequent formation of periderm. No 

 secondary wood has been observed in the stem, but in 

 a Stigmaria described by Professor Weiss, probably 

 belonging to the same plant, extensive secondary 

 growth took place (see p. 257). 



Still more recently Mr. D. M. S. Watson 2 has identi- 

 fied the cone of Bothrodendron mundum in structural 

 material. The cone is a small one, less than a centi- 

 metre in diameter, and is hermaphrodite, with the 

 microsporangia above and the megasporangia below. 

 The sporophylls are short in the radial direction, and 

 the sporangium is attached by a narrow neck of tissue 

 to the middle of the horizontal portion ; there is a large 

 ligule in the usual position. Each megasporangium 

 was found to contain only four megaspores, which are 

 characterised by their long branched spines. The cone 

 is evidently quite distinct from a Lepidostrobus, though 

 apparently nearer to that genus than to Spencerites. 



Bothrodendron is further of interest from the extra- 



1 "Organisation of Fossil Plants of Coal-measures," Part xvi., Phil. 

 Trans. Roy. Soc. B, 1889. 



2 "The Cone of Bothrodendron mundum" Mem. and Proc. Manchester 

 Lit. and Phil. Soc. vol. lii. Part i. 1908. 



