43 ^ Scott .— The Structure of Mesoxylon multirame. 
cut in a transverse section almost at the same point of their course. That the 
leaf-bases were fairly crowded is shown by the tangential section 2344 
(PI. XI, Fig. 6). Twenty-six traces were actually observed in the transverse 
series, representing less than two inches of stem ; the true number in this 
length was obviously greater, as the first three sections are very incomplete. 
It has not been possible to determine the phyllotaxis in this specimen ; the 
number of orthostichies, provisionally estimated at thirteen in the Preliminary 
Note, was no doubt higher—-possibly twenty-one, though the observed 
divergences do not agree with an phyllotaxis. 
M. multirame , like M.poroxyloides, is derived from the ordinary coal- 
balls or seam-nodules, occurring in the actual coal. The preservation of 
the type-specimen is decidedly good, though not equal to that of another 
specimen, since discovered, which will be referred to later. 
The pith has the usual discoid structure with a persistent outer zone. 
The twin bundles of the leaf-trace, unlike those of M. poroxyloides , do not 
fuse immediately on reaching the edge of the pith, but run down side by 
side for some distance; fusion, in so far as it takes place, is a less simple 
process. The centripetal xylem is fairly well developed as long as the 
trace remains double, but disappears about at the level where the strands 
become merged. The secondary wood, phloem, and pericycle agree very 
nearly with those of M. poroxyloides. The outer cortex has the usual 
Dictyoxylon structure, which in the type-specimen is very well differentiated. 
The subdivision of the leaf-trace, in passing through the cortex, into eight 
bundles is clearly shown. 
A great feature of the species is the presence of axillary shoots. In 
the type-specimen they are present in connexion with 19 out of the 26 leaf- 
traces observed in the transverse series; they appear to be absent from the 
7 traces towards the top of the piece of stem, so they were no doubt 
definitely localized. Their peculiar structure, very different from that of 
the axillary buds of M. Sutcliffii, will be described below (p. 442). 
All the best-preserved specimens of M. multirame show axillary shoots, 
but this cannot be used as a specific character, for we cannot doubt that 
if more material of M. Lomaxii and M. poroxyloides were available, these 
species also would prove to have branched in a similar manner. 
The Pith. 
In the type-specimen the pith is only moderately well preserved ; it is 
much more perfect in the large stem to be described later. The structure 
is of the ordinary discoid type (PI. XIII, Fig. 17), not compound, as observed 
in M, poroxyloides. The more internal cells of the persistent zone, so far 
as they are preserved, appear nearly empty, while those of the outer part 
are filled with dense, dark-brown cell-contents (PI. XI, Figs. 2, 5). Most of 
the cells are more or less elongated vertically, and this is especially the case 
