443 
Scott.—The Structure of Mesoxylon multirame. 
a leaf-trace. Similar bodies are shown in two other cases, but it seems 
certain that their separation from the compressed stele is merely accidental. 
The pith is here practically obliterated ; in cases where it is rather 
better preserved ‘ secretory sacs 5 with black contents are evident. Centri¬ 
petal wood has not been recognized, and it is very doubtful if it was 
present ; the centrifugal wood has about five tracheides in each radial 
row. Where the section is oblique we find that the tracheides are 
scalariform or spiral, not pitted. The phloem-zone is ill-preserved. The 
cortex is on the whole of uniform parenchymatous structure, the cells 
becoming smaller towards the outside ; many elements with brown contents, 
perhaps secretory, are present. In the abaxial half of the shoot, tangential 
divisions have taken place, both in the inner and middle regions of the 
cortex. A small-celled epidermis can be traced in many places. 
The flattened form of the stele is constant and evidently, in the main, 
natural, the other tissues showing no sign of compression or distortion. 
The pith is, however, somewhat more compressed than is natural, as shown 
by its better preservation in some sections than in others. This excessive 
compression may be due to growth of the cortical tissues of the shoot, 
indicated by the frequent occurrence of tangential divisions. 
The axillary stele is a good deal better preserved where it has entered 
the cortex of the stem (PI. XIII, Fig. 21). Its sectional form is here no 
longer flattened, but simply elliptical, measuring, in the example figured, 
about 1-5x 0*75 mm. This section is cut at the level where the axillary 
stele has just traversed the cortex and its pericycle is in contact with that of 
the stem. The pith shows some signs of compression, owing, no doubt, to 
the secondary growth of the stele in a confined space. Dark (secretory ?) 
elements are present, as before. Groups of thick-walled elements at the 
inner edge of some of the xylem-wedges seem to represent the centripetal 
xylem,but I have not been able to determine the position of the protoxylem, 
so this interpretation is by no means secure. The centrifugal wood has 
a thickness here of 8-10 elements. It is arranged in definite wedges, the 
medullary rays between them being broad, owing partly to the size and 
partly to the number of their cells ; though most of the rays appear to be 
uniseriate, some are three cells wide. 
The phloem-zone is well developed—quite half as thick as the wood ; 
in this region the cells of the rays are often tangentially dilated. The zone, 
with numerous dark-brown elements, beyond the phloem may be regarded 
as pericycle, but is not well defined. 
The axillary stele as it passes through the cortex has essentially the 
same structure in M. multirame as in M. Sutclijjii (cf. PI. XIII, Fig. 21, with 
Maslen, 1911 , PI. XXXIV, Fig. n), though on a smaller scale in the latter 
species. The shoots, however, when they become free are totally different, 
the little leafy buds of M. Sutclijjii , with a cylindrical axis and cylindrical 
