Seward . — On the genus Myeloxylon ( Brong .). 1 1 
In Fig. 2 at J may be traced the elliptical outline of a 
section, cut obliquely : this is another fragment of Myeloxylon , 
in which the bundles have suffered less displacement than in 
the larger section, and the state of preservation is on the 
whole better. Thick-walled cells occur on the xylem-side of 
some of the bundles ; and the tracheids appear to be reticulate 
and scalariform. 
In this fragment we have a connecting link between the 
larger and smaller specimens, and an additional argument in 
favour of referring all the pieces preserved in the block shown 
in Fig. 2 to the same plant. From the above descriptions it 
is clear that there are a few points of difference between the 
large and small specimens. In the smaller fragment the 
bundles are more distinctly collateral ; there are thick-walled 
cells, sometimes in a continuous row, on the xylem-side 1 ; 
the canals are more numerous and larger than in the section 
figured in Fig. 3 : but, in spite of these differences, we may 
include both specimens in the genus Myeloxylon and in the 
type radiata as instituted by Renault. Although many of 
the xylem-groups of the larger specimen occupy a position 
suggestive of concentric bundles, there are others, whose 
preservation is more perfect, which point with equal force to 
collateral bundles ; and, on the whole, it seems reasonable to 
conclude that the apparently concentric structure is the result 
of the xylem-tracheids becoming detached from the surround- 
ing parenchyma: originally, we may assume, the bundles 
were collateral. We shall find in nearly all specimens of 
Myeloxylon there are certain peculiarities ; but, in dealing 
with such broken fragments of petioles, it is better to err on 
the side of including too many varieties under one general 
type than to attempt to define new species upon insufficient 
data. We are ignorant as to how far the structures of a 
Myeloxylon-xxis of higher order differs from that of a lower 
1 As already remarked, similar mechanical elements are indicated in the large 
fragment : no doubt the worse state of preservation of this specimen is to some 
extent responsible for apparent differences between its structure and that of the 
smaller and more perfectly preserved fragment. 
