THE CARBONIFEROUS FLORA OF BERWICKSHIRE. 269 
(fig. 31), while others are narrow, greatly elongated, and somewhat swollen at the end 
(figs. 30 and 4). They do not seem to be produced by any crushing or folding of 
the outer tissues. It is possible, however, that they may represent transverse sections 
of longitudinal ridges. The epidermis of the midrib is well preserved as a definite 
layer of rather small cells. 
Judging from a fragment present in the original block found by Mr Marueson, 
the lamina of the leaf must have been of considerable thickness (fig. 24). The 
epidermis is quite distinct, but no stomata could be distinguished in it. There were 
indications of a hypodermal zone of sclerotic strands on both sides of the leaf, and 
resin sacs were very plentiful in the mesophyll. In the fragment in question the 
vascular bundles lie in single row, but in others less well preserved they appear to be 
irregularly scattered. 
Remarks on other Stems of Stevomyeton. 
A few other stems were present in Mr Maruxson’s material which in all essential 
points resemble the specimen already described, but they exhibit a few features of special 
interest, to which it is necessary to refer. 
In one of these stems the primary xylem at first sight gives the impression of being 
parenchymatous (figs. 26-27). We were able to satisfy ourselves, however, that this is 
not the case. The apparent parenchyma cells are really trachez that have undergone 
a certain amount of decay. In this section also the three lobes of primary xylem 
appear to be quite separate from one another, but this, again, is probably due to 
decay (fig. 26). 
In another stem (fig. 29) the secondary thickening has only just begun. It is 
present in greatest quantity opposite the sides of the triangle of primary xylem, and has 
not yet crossed over in front of all the lobes. 
Again, an unusually small stem was found in which the primary xylem only measures 
2°5 mm. at its greatest width (fig. 5), while the secondary xylem is much more ex- 
tensive than it is in the stem shown in fig. 29, which is photographed at the same 
magnification. This indicates that, apart from secondary thickening, the primary axes 
of Stenomyelon were of different sizes, which might perhaps suggest that the plant was 
branched. 
CoNCLUSION. 
The stem of Stenomyelon possesses so many features peculiar to itself that in the 
present state of our knowledge it is unsafe to enter into any speculation as to its relation- 
ship to other members of the Cycadofilices. It is perhaps best to let it remain among 
that nebulous group in which it has been already provisionally placed by Dr Scorr.* 
At the same time it should be noted that the absence of independent meristeles in the 
* Studies in Fossil Botany, 2nd ed., part ii. p. 498, 1909. 
