382 Watson . — On Mesostrobus , a New Genus of 
a curve downwards, forming a sort of pocket, the upper surface of which is 
richly lined with transfusion tracheids. This pocket surrounds the base of 
the ligule, which is set in a deep pit, over the edge of which its tip probably 
did not rise. 
I believe that in this region the parichnos bifurcates, at any rate there 
are two patches of tissue, one on each side of the vascular bundle, which are 
often defective, and when present resemble in appearance some examples of 
the parichnos of Lepidodendron leaf-bases ; these areas are, however, less 
well defined than the parichnos of ordinary leaf-bases. 
The lamina takes its rise from the upper surface of this mass, and has 
on its inner surface a groove, which is the continuation of the ligular pit 
(Phot. 7 gr). This groove is exactly similar to one which is a very 
characteristic feature in the sporophylls of Bothrodendron mundum . 
The vertical part of the lamina is of very simple structure, being regu- 
larly lenticular in transverse section, and having a single vascular strand up 
the middle (Phot. 7). The main mass of the leaf is composed of ordinary 
parenchyma limited on the outside by a single layer of cells which forms 
the epidermis. The vascular bundle, which is central in position, is sur- 
rounded by a small amount of transfusion tissue consisting of the familiar 
short tracheids, with the dimensions of an ordinary parenchymatous cell and 
spiral thickening. The structure of the bundle is apparently quite simple, 
but cannot be made out in detail. Just to the outside of the bundle is a rib 
of sclerized tissue of quite small dimensions, running straight up the 
lamina, which, as a whole, tends to become sclerized towards the tip. The 
cells to the sides of the transfusion tissue sometimes have dark walls ; they 
may have been secretory cells of some sort. 
The sporangia are inserted on the upper surface of the horizontal 
portion of the sporophyll, and their attachment extends from just inside 
the ligule to a spot rather more than half the length of the horizontal 
portion from the axis (Phot. 1, 4, and 5). They are thus only attached to 
the distal half of the sporophyll. Their attachment is narrow tangentially, 
exactly resembling in this respect that of Lepidostrobus (Phot. 5). Diagram 1 
will convey a much clearer idea of this arrangement than any amount of 
description. 
In the actual cone under consideration the sporophylls incline down- 
wards, and I think that this character is normal, and not the result of post- 
mortem crushing; at any rate this inclination enables one to settle the 
question of the length of the attachment of the sporangium quite definitely, 
for it gives a series of sections across the upper surface of the sporophyll at 
measurable distances from the axis. 
The sporangia are not well preserved, but their wall appears to be only 
one cell thick, and of the normal Lepidostrobus type. In section parallel 
to the surface, however, the cells (although isodiametric) are seen to be 
