520 Note. 
furrows, but is thicker on the lower side ; otherwise the mesophyll is made up of rather 
large, isodiametric cells. 
The vascular tissue lies within a definite central region about 960 jx wide by 
480 fx deep, which is well defined, but not marked off by any evident sheath. 
There are two vascular bundles with their xylem-groups widely separated, the distance 
between them being 280^, while the maximum diameter of each xylem-strand is 
under 200 /x. The xylem-strands are embedded in thin-walled tissue, in which the 
limits of the phloem cannot be distinguished in transverse section. Below each 
bundle is a broad band of dark, apparently sclerotic tissue, perhaps identical with 
the ‘ gaine ' of M. Renault’s description. In the median line of the leaf and below 
the level of the bundles is a gap in the tissue, exactly agreeing in position with the 
lacuna or strand of delicate tissue figured by M. Renault in the leaf-traces and leaves 
of Sigillaria 1 . 
The transfusion-tissue (‘ tissu vasiforme * of M. Renault), consisting of 
reticulate tracheides, is extremely well developed, and forms a horseshoe, embracing 
the whole lower side of the central region, and approaching the bundles at its two 
upper extremities. Thus the whole structure of the leaf, apart from the presence of 
two bundles instead of one, is altogether that of a leaf of one of the Lepidodendreae ; 
the analogy with certain Coniferous leaves is striking, though probably quite uncon- 
nected with affinity. 
The other leaf in the Shore slide was evidently cut near its tip. The width is 
i *7 mm. and the maximum thickness only igo/x. The lateral furrows are scarcely 
indicated ; it is sufficient to say that here also the two vascular bundles are quite 
separate, with a group of thick-walled tissue between them. 
Of the Dulesgate specimen there are four successive sections, passing through 
the same leaf (Nos. 1166-1169 in my collection), but there is little change of structure 
throughout the series. The leaf has a different sectional form from that of the 
Shore specimen, for the upper surface is markedly concave, giving some of the 
sections a U-shaped outline. A sharp median depression is present on the upper 
side and a narrow dorsal rib on the opposite surface. There is very little trace of 
lateral furrows, but the hypoderma is interrupted at points corresponding to them. 
Here also palisade-tissue is present towards the upper surface. The central region is 
less well defined than in the Shore leaf ; the two vascular bundles are quite separate, 
though not so far apart as in that specimen ; the space between the two xylem-groups 
is about 1 40 fx wide, the xylem-groups themselves having a maximum diameter of 
about 260 fx. Transfusion-tissue is present, chiefly towards the lower side, as in the 
first specimen. 
Another leaf is cut in obliquely longitudinal section ; I have not yet been able 
to make out any pitted elements for certain. 
The Dulesgate specimen makes the impression of being less highly differentiated 
than that from Shore ; it is possible that all the sections of the former were cut from 
the apical part of a large leaf, but of course it is quite doubtful whether the two 
specimens belonged to the same species. 
1 Tiges de la flore carbonifere, PI. 12, Fig. 1 ; Flore foss. d’Autun, &c., Pt. 2, PI. XLI, Fig. 7, e ; 
Figs. 12-14; Figs. 18 and 19, r. 
