206 



DE. AGNES AEBER ON THE 



Finally, I wisli to express my gratitude to Professor T. McKenny Huglies, P.E.S 

 ho has given me every facility for carrying out this work in the Sedgwick Museum. 



2. A Survey of our Present Knowledge op the Structure 



OP Lepidosteobus. 



The general characters of tlie cone-genus Lepidostrolms are too familiar to need 

 capitulation here. In all essentials this genus is a remarkably uniform one. 



one. We are 



fortunate in having a fairly complete knowledge of several species which have been 

 found in the petrified state, and it may he useful, before dealing with the ohservations 

 contained in the later sections of the present paper, to refer very hriefly to these cones 

 and their structure. 



One of the first Lepidostrohi of which the internal structure hecame known, was 

 L. Brow7iii, (linger) Schpr., a large cone from the Lower Carboniferous rocks, which 

 was originally described by Eobert Brown *. We have recently heen put into possession 

 of detailed knowledge of this species, and of one or two other cones closely related to it, 

 hy means of Zeiller's f exhaustive and heautif ully illustrated monograph. The strobilus 

 has several peculiar features, the most striking of which are the following : the 

 lamina of the sporophyll terminates in a swollen cushion, and traheculse of sterile 

 tissue arise from the floor of the sporangium and penetrate among the spores. No 

 megaspores have been discovered. 



Another Lower Carboniferous cone whose structure is preserved is Lepidostrohus 

 Veltheimianus, Scott, a heterosporous form from the Calciferous Sandstone of Burnt- 

 island, first described by Williamson J. This is a small and slender cone, similar in 

 general structure to the famili;ir Z. oldhamius of the Coal Measures. A delicate radial 

 plate of sterile tissue arises from the floor of the microsporangium, and penetrates 

 some distance into the sporangial cavity. 



From the Calciferous Sandstone we have also another heterosporous cone, Lep'ido- 

 stt'obus Wunschianus . The structure of this strohilus was described and figured by 



Binney §, not, however, in microscopic detail. 



The best known Lepidostrobus^ which occurs as a petrifaction in tlie Upper 

 Carhoniferous rocks, is the Coal Measure form L. oldhamius, originally descrihed by 

 Williamson || . Binney % at an earlier date, had described and figured, under the name 

 of Lepidodendron Earcourtii, sections from the identical specimen upon which 

 Williamson afterwards based the species oldhamius. Binney also descrihed other 

 sections of the same type of cone, attrihuting them to L. vasculare. More recently 

 Maslen ** has redescribed Lepidostrohus oldhamius in detail, with special reference to 

 Williamson's slides. The cone of this species is larger than that of L. Veltheimianus, 

 hut smaller than that of L. Brownii. No megasporangia have been up till now 



* Brown, E. ('48) and ('51). For another early account of some members of the genus see Hooker, J. D. ('-i^^)- 

 t Zeiller, E. ('11). ' + WilHamson, W. C. (73), p. 294 and pi. 44. § Binney, E. W. (71), pi. H- 



II WUliamson, W. C. ('94), pp. 27 & 28, pi. 9. fig. 58, pi. 6. figj. 61 & Q2. 

 t Binuey, E. W. (71), p. 46 etc., and pis. 7 & 8. ** 3Iaslen, A. J. ('99). 



