46 LYCOPOPIALES [CH. 



This is well shown in the section of a cone of L. clavatum shown 

 in fig. 126, F. The sporangia a and h are cut through in an 

 approximately median plane showing the irregular outline of 

 the sterile pad (p) of tissue in the sporogenous cavity. Those 

 at c and d have been traversed at a lower level and the two 

 lobes of the saddle-shaped sporangia are cut below the attachment 

 to the sporophyll. The distal laminae of the sporophylls, cut 

 at different levels, are seen at the periphery of the cone. 



In longitudinal radial section of some cones the sporangia 

 appear to occupy an axillary position, but in others {e.g. 

 L. clavatum) they are attached to the horizontal portion of the 

 sporophyll almost midway between the axis of the cone and the 

 upturned distal end of the sporophyll (fig. 126, D). The wall 

 of a sporangium frequently consists of 2 — 3 cell-layers and in 

 some cases {e.g. L. dichotomum), it may reach a thickness of seven 

 layers, resembling in this respect the more bulky sporangia 

 of a certain type of Lepidodendroid cone. The sporogenous 

 tissue is separated from the stalk of the sporangium by a mass 

 of parenchymatous tissue which may project as a prominent 

 pad (fig. 126, D, F, p) into the interior of the sporogenous 

 cavity. This basal tissue (the subarchesporial pad of Bower ^) 

 has been observed in L. clavatum to send up irregular processes 

 of sterile cells among the developing spores, suggesting a 

 comparison with the trabeculae which form a characteristic 

 feature of the sporangia of Isoetes and with similar sterile 

 strands noticed by Bower'' in Lepidostrobus (cone of Lepido- 

 dendron). 



Each sporophyll is supplied by a single vascular bundle 

 which according to published statements never sends a branch 

 to the sporangium base. The fertile tips of the foliage shoots 

 of L. cernuum (figs. 126, A — C) afford good examples of 

 specialised cones. The surface of the cone is covered by the 

 broadly triangular laminae of sporophylls (fig. 126, C) which in 

 their fimbriate margins resemble the Palaeozoic cone-scales 

 described by Dr Kidston^ as Lepidostrobus fimbriatus. The 

 distal portions of the sporophylls are prolonged downwards 



1 Bower (94). 2 j6j^_ (94) pi_ xLym, 



3 Kidaton (83) PI. xxxi. figs. 2—4. 



