12 Seward. — On the genus Myeloxylon ( Brong .). 
order ; that branching does occur we know from the figures 
and descriptions of Renault 1 . Slight differences in structure 
may in some cases be the result of differences in fossilization ; 
and further, as Thomae 2 has pointed out, in speaking of fern- 
petioles, it is hopeless to attempt to determine species by 
trusting to the anatomical details of detached fragments. 
The various specimens, therefore, described in these notes are 
referred to Myeloxylon radiata because of the possession of 
important characters in common. It is quite possible that 
further additions to our knowledge will render advisable the 
creation of additional species. 
Specimens from Prof. Williamson’s Collection. 
One of the slides 3 lent to me by Prof. Williamson shows 
very clearly the essential characters of Myeloxylon : these 
characters are much more clearly defined in this specimen 
than in the other examples described by Williamson to which 
I have previously referred. In this section, prepared from an 
Oldham specimen, the collateral bundles are very distinct, 
but, as generally happens, the phloem has not been preserved : 
thick-walled mechanical elements form an almost continuous 
ring round the xylem-groups. Another specimen of Myelo- 
xylon from Oldham, in the Binney collection, agrees closely 
with Prof. Williamson’s, but surpasses it in preservation ; this 
will therefore be described at greater length. 
Specimen from the Binney Collection. 
In this collection, now in the Woodwardian Museum, Cam- 
bridge 4 , I have found two slides of Myeloxylon , the one a 
transverse, the other a longitudinal section, which throw 
some fresh light on the nature of the vascular bundles. 
In the transverse section, which measures 3 cm. in its longest 
part and 17 in its broadest part, the bundles have much the 
1 Renault, Etude du genre Myelopteris , PI. V. Fig. 42. 
2 Thomae, Die Blattstiele der Fame tPringsh. Jahrb. XVII. 1886, p. 158). 
3 Number 286 in Prof. Williamson’s Catalogue. 
4 For the loan of this specimen I am indebted to Prof. McKenny Hughes. 
