LEPIDODENDREAE. 



233 



The study of the impressions has revealed the main features in the 

 organisation of these cones. The straight usually tolerably thick axis, 

 which is bifurcated in one instance only \ bears all round it sporophylls 

 closely crowded and exactly like one another, on each of which can be 

 distinguished the peculiarly developed leaf-base (the cushion of the vege- 

 tative homologue), the single sporangium attached to it, and the lamina. 

 The leaf-base, the characteristic features of which are correctly described 

 by Stur 2 , is developed in the form of a long pyramid scarcely narrowing 

 upwards and sometimes winged on the sides, which stands out at a right 

 angle from the axis ; its cross section is transversely rhombic and flattened 

 in the median direction ; it bears on its upper side the cylindrical usually 

 very capacious sporangium, which is bluntly rounded at the extremity, and 



FIG. 25. Fructifications of Lepidodendron. A transverse section of the cone of Lepidostrobus Brownii, Schpr, 

 showing in the centre the axis and the bundles on their way to the leaves ; next to these are the sporangia in 

 longitudinal section, and beyond them several layers of transverse sections of the erect apices of sporophylls of 

 lower insertion. B longitudinal section of the apex of the same cone. C diagrammatic longitudinal section of a 

 Lepidostrobus ornatus, Hook. D a detached fertile leaf (Lepidophyllum) seen from above, the basal portion separated 

 by a transverse fold from the originally erect apex ; the sporangium was attached to its median line. A and after 

 Schimper. C after Hooker. D after a specimen in my possession collected by myself in the Gerhard mine at 

 Saarbriicken. 



sometimes even allows the spore& to be seen in it. Binney's 3 figures should 

 be consulted. The usually lanceolate lamina is attached by its entire breadth 

 to the top of the leaf-base, and bends upwards so as to be parallel to the 

 axis, and to overlap and cover the laminae next above it like a tile on a roof, 

 while the outer extremity of the sporangium is close against its inner surface 

 (Fig. 25 B\ Sometimes its sharp lower margin projects beyond the top 

 of the leaf-base, so that a somewhat peltate attachment results, as in 



Lindley and Hutton (1), vol. iii, t. 163. 



Stur (5), p. 233. 



Binney (1), II, tt. 9, 10. 



