XV] LEPIDOSTROBUS 185 



Each vascular bundle consists of a strand of xylem, apparently 

 of mesarch structure, accompanied by a few layers of paren- 

 chyma on its outer face and by a group of cambiform elements, 

 the whole being enclosed in a sheath of parenchyma continuous 

 with the inner cortex of the cone axis. The vascular bundle is 

 accompanied by a parichnos in the outer cortex and in the 

 sporophyll. 



There can be little doubt that the Palaeozoic Lepidodendra, 

 like Lycopodium cernuum (fig. 123) and other recent Lycopods, 

 usually bore their cones at the tips of slender shoots. The 

 fertile shoot of Lepidophloios scoticus shown in fig. 160, B, affords 

 one of several instances supporting this statement; similar 

 examples are figured by Brongniart^ Morris', and by more recent 

 writers. The apparently sessile cone figured by Williamson" 

 from a specimen in the Manchester Museum is certainly not 

 in situ, but is accidentally associated with the stem. 



The general absence of secondary wood in the steles of 

 Lepidostrobi is, as Dr Kidston'' points out, consistent with the 

 view that the cones were shed on maturity and that fertilisation 

 probably took place on the ground, or perhaps on the surface of 

 the water where the slender hairs of the megaspores (fig. 191, 

 F, I) may have served to catch the microspores. 



Reference has already been made to the belief on the part 

 of some palaeobotanists that the large scars of Ulodendron 

 represent attachment-surfaces of sessile cones, and reasons have 

 been given against the acceptance of this view. 



There is considerable rang« in the size of Lepidostrobi. An 

 incomplete specimen, 33 cm. long and 6 cm. broad, which 

 may have been 50 cm. in length, is described by Renault and 

 Zeiller" from the Commentry Coal-field. The larger cones 

 afford a striking demonstration of the enormous spore-output 

 of some species of Lepidodendron. 



Among the earliest accounts of the anatomy of Lepido- 

 strobus are those by Hooker' and Binney^ One of the specimens 



1 Brongniart (37) PI. xxiv. ^ Morris (40) PL xxxviii. fig. 10. 



3 Williamson (93) PI. vi. fig. 26, A. * Kidston (01) p. 62. 



» Benault and Zeiller (88) A. PI. lxi. fig. 4. « Hooker (482). 



7 Binney (71). 



