439 
Scott.—The Structure of Mesoxylon multirame. 
with the outermost pith-cells which border on the wood. These cells, like 
their neighbours, usually have dark contents. The cells of the diaphragms 
are much larger and have a different shape, their greater diameter being 
horizontal. In the middle part of the diaphragms the cells have collapsed 
and their walls are often torm 
As usual the diaphragms became much thicker towards the periphery. 
In this case, however, there is often a constriction between the thickest part 
of the diaphragm and its abutment on the persistent outer zone. Two 
adjacent diaphragms sometimes unite in this region—a slight approach to 
the compound condition found in M. poroxyloides. There is no important 
difference in pith-structure between M. multirame and M. Sutcliffii. 
The Leaf-traces. 
The most valuable feature of the type-specimen is the clear way in 
which the leaf-traces are shown at all points of their course. In a good 
transverse section, such as that shown in PI. XI, Fig. i, many traces can be seen 
in various positions; but probably the best way to deal with the subject of 
their course will be to take-some one trace and follow it downwards through 
a series of transverse sections. The illustrations, however, are from different 
traces, selected as showing the structure best at the various levels figured, 
for of course we cannot expect the same trace to be equally favourable at 
all points of its course. 
We will take the trace which is numbered 13 in the diagram, PL XIII, 
Fig. 16. 
This first appears in section 2335. 
Naturally the axillary shoot precedes the subtending trace in approach¬ 
ing the stem and is alone seen in this section (PI. XI, Fig. 2). The shoot is 
here partly attached to the cortex of the main stem. It shows the usual 
extremely flattened stele and parenchymatous cortex with no visible appen¬ 
dages. Three such steles are shown, as it happens, in this section—they are 
all represented in the photograph, PL XI, .’Fig. 2, and the best of them more 
in detail in the drawing, PL XIII, Fig. 22. The stele measures about 3-5 mm. 
in length (tangential to main stem) by scarcely 0*25 mm. in width. 
In the next section below (2334) (diagram, PL XIII, Fig. 16), the axillary 
shoot has completely joined on to the stem and its stele is seen about half¬ 
way through the cortex. The subtending leaf-base has now appeared 
(though badly preserved) to the exterior of the axillary stele, and at least 
7 of the 8 bundles of the leaf-trace are recognizable (see diagram, PL XIII, 
Fig. 16, and cf. Fig. 18). The axillary stele is here less flattened, its dimen¬ 
sions being about 2*5x0*75 mm. (cf. the detailed drawing of another stele 
in Fig. 21). 
Proceeding downwards, section 233d shows the axillary stele (here 
little more than 1*5 mm. in tangential diameter) in the phloem-zone, but its 
