1 6 Scott. — On the Fertile Shoots of 
pericycle are poorly preserved, and the inner cortex, which alone is present, 
shows a not very distinctive parenchymatous structure. 
On the data available it appears that this specimen is a stem allied to 
Mesoxylon ; the size, and especially the considerable development of the 
wood, indicate that it was an ordinary vegetative shoot. 
The second specimen (section 2993) is of a much larger stem (PI. II, 
Fig. 13). Only the pith and wood are preserved, and the latter is incom- 
plete. The maximum radius, to the outer edge of the wood, is almost 
2 cm. The pith is about 6 mm. in diameter ; it is nearly complete, but 
it is quite likely that the plane of section may happen to coincide with 
a diaphragm. Its contour is obscurely angular. The structure is very 
uniform, the cells merely becoming smaller towards the outside ; many 
of them have dark contents. The appearance is very similar to that of 
a diaphragm of Mesoxyton multirame when seen in horizontal section. 
The structure of the wood is the same as in the former specimen, 
except that the rays sometimes appear to be biseriate, a feature often met 
with in species of Mesoxylon . It shows a more definite appearance of 
4 annual rings ’ than is usual in carboniferous woods ; examined with a lens 
the rings look quite like concentric bands of autumn wood (PI. II, Fig. 13). 
But they prove, on closer investigation, not to be really continuous, and 
though some of the cells are flattened this is not at all generally the case. 
The distinction appears to depend mainly on a somewhat greater thickness 
of the cell-walls in these bands. 
Two single leaf-traces are seen passing out obliquely through the inner 
part of the wood (PL II, Fig. 13). 
At several points of the inner edge of the wood a prominent group of 
primary xylem is seen, which is evidently centripetal in development, and 
comparable to the primary xylem of a Mesoxylon (PI. II, Fig. 14). In all 
cases such groups occur singly, never in pairs ; they clearly represent the 
downward continuation of single leaf-traces which have passed in at a higher 
level. 
Discussion . 
These two specimens differ practically in nothing except size, and may 
safely be referred to the same species. The characters open to investigation 
are somewhat meagre ; in the general structure of the wood and pith 
(when shown) and in the presence of centripetal xylem, both in the outgoing 
leaf-traces and in strands at the inner edge of the wood, the stems agree with 
Mesoxylon. They differ from that genus in the important point that the 
leaf-trace, as it traverses the wood, is single and not double. At the same 
time it is evident that the specimens are ordinary vegetative stems, and thus 
directly comparable with those on which the genus Mesoxylon was founded. 
It will be noticed that the pith is smaller than is usual in Mesoxylon . 
