454 Scott—The Structure of - Mesoxylon multirame. 
or scalariform. Bordered pits in the rest of the wood usually in two rows. 
Tangential pits present in places. 
Medullary rays 1-12 cells in height, usually uniseriate. Ray-cells 
pitted on radial walls. Xylem-parenchyma occasionally present. 
Phloem consisting of resiniferous (?) tubes, parenchyma, and sieve-tubes. 
Phloem-rays dilated. 
An axillary shoot present in many of the leaf-axils. Shoot leafless, 
with a flattened stele, branching distichously, the branches bearing scale- 
leaves or bracts. 
Seam-nodules, Shore, Littleborough. Lower Coal Measures. 
It will be noticed that this diagnosis differs in several respects from the 
one originally given (Scott and Maslen, 1910, p. 238 ). It has been some¬ 
what expanded as regards the leaf-traces, the wood, the phloem, and the 
axillary shoots. On the other hand, the cortical characters have been left 
out, as they seem to afford no real distinction. 
The only really important differences from M. poroxyloides are in the 
course of the leaf-traces in the wood and in the axillary steles. The former 
is a definite and presumably constant distinction; the latter is probably 
more of biological than taxonomic significance. When we know M. poroxy¬ 
loides better, we shall no doubt find that it sometimes produced some form 
of axillary shoot, and we have seen that such shoots are not everywhere 
present in M. multirame. As already stated, it is highly probable that the 
type of axillary shoot characteristic of this species was connected with 
reproduction. 
From M. Lomaxii the distinctions are obvious, both in the course of the 
bundles and the structure of the inner part of the wood. 
The latter character also distinguishes M. multirame from M. Sutcliffiiy 
which further differs widely in the nature of the axillary shoots. This, 
however, as already pointed out, may be a matter of function rather than of 
specific distinction. 
In the new diagnosis the comparison of the axillary shoot with a 
phylloclade is omitted, as it might be misleading, now that we know that 
the shoot represented a branch-system. 
The points of more general interest are: The presence of tangential 
pits on some of the tracheides; the occasional presence of xylem-paren¬ 
chyma ; the structure of the phloem, consisting of more or less concentric 
bands of secretory sacs (probably resiniferous), sieve-tubes, and parenchyma; 
the lateral connexions of the axillary stele and its frequent division into 
two in passing inwards through the wood ; the distichous branching of the 
axillary shoots, the branches bearing scale-leaves or bracts, and also, 
possibly, secondary branches. 
On the whole the characters observed in this species accentuate the 
relation of the genus Mesoxylon to Cordaites (Renault, 1879, 1896), but it is 
