14 Seward. — On the genus Myeloxylon [Brough). 
some cells of the ground-tissue. In Fig. 17 another bundle 
is represented in longitudinal section : the phloem-elements 
are imperfectly preserved at P ; next to them is a well-marked 
spiral tracheid, and following this what appears to be a second 
spiral element with larger scalariform and reticulate tracheids. 
Having described at some length these specimens referred 
collectively to Myeloxylon , it only remains to consider briefly 
such facts as may help us in attempting to assign this palaeo- 
zoic fossil to its natural position in the plant-kingdom. 
We may summarise, and briefly discuss, the arguments 
advanced by those who have referred Myeloxylon to the 
Marattiaceae. 
1. The association of Alethopteris-/?*^? with Myeloxylon, 
and a close agreement in their anatomical characters. 
The figure which Renault gives in support of his statement 
that Alethopteris- pinnules have been found attached to a 
rachis having the structure of Myeloxylon is scarcely con- 
clusive : so far as one can judge from the section represented 1 , 
it is by no means obvious that the structure is the same as 
that of Myeloxylon. If, however, it is found that Alethopteris 
undoubtedly possesses this type of structure, we have no proof 
that in transferring it from the Ferns to the Cycads we shall 
be assigning it to a position to which it has no claim 2 . 
2. The branching habit of Myeloxylon. 
Renault has given proof of this in his figures and descrip- 
tions of French specimens. Although Bowenia , as Solms 
reminds us, is the only recent Cycad in which the frond is 
branched, yet this solitary instance in living Cycads is not 
insufficient when we are dealing with plants of palaeozoic 
times. In such specimens as I have examined, no signs of 
branching have been detected. 
3. The vascular bundles , &*c. 
It has been pointed out that Myeloxylon agrees in its bundles 
1 Renault, Cours de bot. foss. vol. III. PI. 27, Fig. 12. 
2 Since this was written I have found some specimens in the Binney collection 
which.it is hoped, will afford further evidence in reference to Myeloxylon-^AxmxAz*,. 
