Seward . — On the genus Myeloxylon ( Brong .). 1 3 
same disposition as in the large specimen from the Millstone 
Grit ; those near the periphery form a fairly distinct ring, 
whilst the others appear to have no definite arrangement. 
The hypoderm is of the normal type of Myeloxylon radiata , 
and need not be further considered. Canals are numerous 
and possess characters such as have already been described. 
Many of the bundles are of the type shown in Fig. 13 ; here 
we find, for the first time, not only the xylem but also the 
phloem intact. In this particular bundle the smaller proto- 
xylem- elements are not quite so clearly marked as in most 
of the bundles, but the phloem is preserved with exceptional 
distinctness. In Fig. 14 a second bundle is figured ; here the 
phloem is less perfectly preserved, but the small elements of 
the protoxylem are much more distinct : the sheath of small 
parenchymatous cells is clearly shown. In Fig. 15 we have 
another form of bundle, the xylem being in the form of an 
oblong group of tracheids, and the phloem in two distinct 
groups on the same side of the xylem. In all these figures 
thickened mechanical elements are noticed on the xylem-side, 
and the presence of these is a constant character in the 
specimen. The striking resemblance of both these forms of 
vascular bundle to those of recent Cycadean petioles will be 
apparent when we sum up the arguments bearing upon the 
question of botanical affinity. In the longitudinal section of 
the same specimen we find, in two of the bundles at least, 
undoubted confirmation of what has previously been assumed 
but not actually demonstrated, namely, the occurrence of 
protoxylem or spiral tracheids on the phloem-side of the 
xylem. Fig. 16 represents one of the bundles where we 
have large reticulate and scalariform tracheids in contact, on 
one side, with the parenchyma of the ground-tissue, and, on 
the other, separated from the less perfectly preserved phloem 
by distinct spiral tracheids of small diameter. The phloem 
shown at P is not sufficiently well preserved to enable us to 
describe its structure in detail ; it consists of elongated, narrow, 
and broken elements, whose delicate walls have naturally 
suffered considerably during fossilization. At GG are seen 
