XVIIl] BOTHRODENDRON 263 



form as those in Lepidostrobus, but we have no more exact 

 information as to their morphology. A recently published 

 description of a petrified strobilus by Mr Watson affords a 

 welcome addition to our knowledge. There is little doubt that 

 this cone was borne by a species of Bothrodendron; the evidence 

 for this conclusion is supplied by the agreement of the ana- 

 tomical characters of the stele with that of the vegetative shoots 

 originally described by Williamson as Lepidodendron mundum 

 and by the constant association of the cones and vegetative 

 shoots. In 1880 Williamson described a crushed cone containing 

 both megaspores and microspores which he spoke of as " a dimi- 

 nutive organism, reminding us more of the dwarfed fruits of 

 many living Selaginellas than of the large Lepidostrobi^." 

 Watson's specimens enable us to give a more complete account 

 of this type. The axis of the strobilus bears short sporophylls 

 bent upwards into a distal limb with a conspicuous ligule in a 

 deep pit beyond the shortly stalked sporangium. The length of 

 the strobilus is estimated at 10 mm. ; the stele is of the same 

 type as that of Bothrodendron mundum, but it differs from the 

 specimens of the vegetative shoots so far found in having some 

 secondary xylem. As shown in the sketch reproduced in fig. 216 

 each sporophyll is characterised by two tangentially placed 

 grooves, g, on the lower face, and by numerous transfusion 

 tracheids, tr, above the vascular bundle, vb, immediately below 

 the ligule, I. Megasporangia and microsporangia occur on the 

 same cone, the megasporangia being on the lower sporophylls 

 and containing a single tetrad of megaspores. Fig. 219, E, shows 

 a radial longitudinal section of a microsporophyll bearing a 

 sporangium on the adaxial side of the ligule, /, below which is 

 the single vascular bundle and a group of short tracheids at t. 

 The sporangia closely resemble those of species of Selaginella 

 and Lycopodium and, as pointed out by WatsonS they also 

 recall the sporangia of the Palaeozoic genus Spencerites. Both- 

 rostrobus is distinguished from Spencerites by the presence of 

 a ligule, by the structure of the axis, and by the different form 

 of the sporophylls. The occurrence of four spores only in the 

 megasporangia is another character in which the extinct type 

 1 Williamson (80) A. p. 500, PL xv. 8. ^ Watson (08-) p. 12. 



