XVl] SIGILLARIOSTROBUS 217 



cone was probably heterosporous, but megaspores alone have so 

 far been discovered. The sporophylls bear a close resemblance 

 to those of Lycopodium cernuum (fig, 126, C). In some of the 

 illustrations of this type given by Kidston the naked cone-axis 

 with its numerous sporophyll-scars is clearly shown, reminding 

 one of the naked axes of the cones of the Silver Fir (Abies 

 pectinata) or Cedar after the fall of the scales. 



Our knowledge of Sigillarian cones is too incomplete to 

 admit of a detailed comparison with the strobili oi Lepidodendron 

 or with those of recent Pteridophytes. There can, however, be 

 little doubt that Goldenberg^ was correct in his selection of 

 Isoetes as the most nearly allied recent plant so far as the fertile 

 leaves are concerned. It would seem that the sporangia were 

 comparatively delicate structures which have left no clearly 

 defined remains of their walls in the carbonised specimens; 

 Kidston, indeed, speaks of the hollow bases of the sporophylls as 

 holding the spores, but this is hardly likely to have been the 

 case. Our knowledge of the anatomy of Sigillariostrobus is 

 practically nil, but in one specimen of a Sigillaria elegans 

 stem Kidston'' describes the structure of the tissues as seen in 

 a transverse section of a scar of a fertile shoot ; from this we 

 learn that the stele was composed exclusively of primary 

 tracheids forming a solid strand without a pith. It is probable 

 that the cones of Sigillaria were heterosporous, but in no 

 instance have undoubted microspores been discovered; the 

 megaspores in each megasporangium were fairly numerous as in 

 Isoetes (fig. 133, E). In one species, Sigillariostrobus major 

 (Germar), from Permian rocks of France and Germany, Zeiller^ 

 states that the whole of a single cone bore megaspores (0*8 — 1 

 mm, in diameter) only; this is, however, not opposed to the idea 

 of heterospory, as we find instances in Selaginella of strobili 

 bearing one kind of spore only (c£ p. 56). 



In a few instances, it has been possible to correlate cones 

 with certain species of Sigillaria, but in most cases the strobili 

 occur as isolated fossils. 



1 Goldenberg (55). 



2 Kidston (05) PI. in. figs. 23, 25, 26, 27. « Zeiller (06) p. 160. 



