8 
PROEESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
in some of my specimens in the more central parts of the rachis. I have already men- 
tioned that a few fibres occasionally unite with the small parenchymatous cells to 
compose the imperfect sheath of the vascular bundles. But besides these we find free 
bundles, occasionally in contact with a gum-canal. At other times I discover one or 
two such outside, but not far removed from the sheaths of the vascular bundles. Fig. 13 
represents one of these bundles enlarged 350 diameters ; d, d are portions of two of the 
vessels belonging to a large vascular bundle, of which, as we have already seen, e , e is 
the cellular sheath and g is the prosenchymatous bundle composed of thickened fibres 
and imbedded in the medullary parenchyma. In the specimen figured a second bundle 
existed in similar relationship to the vascular bundle d d. 
There yet remains to be considered the branching of these petioles. In fig. 5, which 
in all probability represents one of the ultimate subdivisions of the true rachis, we have 
a distinct branchlet given off at h. From its size I imagine this must have been the 
small petiole of a leaflet ; a second and similar one is obviously being given off at ft!. 
If these are, as I suppose, the ultimate petioles of leaflets, the latter have been arranged 
in this specimen, at least, at intervals of about half an inch apart. In another of my 
examples a rachis of about a quarter of an inch in diameter is giving off a lateral branch 
of about an eighth of an inch in diameter. In both these cases the secondary branches 
are given off at right angles to the primary one, and not obliquely, corresponding in 
this respect to their arrangement in the Myelojpteris Landriotti of M. Renault*. 
In fig. 1 a large cylinder of cellular tissue, with a vascular bundle within it but 
pushed out of its normal central position, is seen at x. This is a small rootlet of 
Stigmaria which, as is so often the case, has forced its way into the ruptured interior of 
the petiole. 
These descriptions will, I think, make it plain to the experienced student of vegetable 
organography that the subject of them cannot be a Palmaceous Monocotyledonous plant. 
The structure of the vascular bundle, especially the restriction of its vascular tissue to 
spiral and barred forms, with the absence of all traces of phloem-structures, makes this 
sufficiently obvious. In like manner, though at first sight its remarkable layer of 
hypodermal woody prosenchyma bears a superficial glance to the peripheral fibre-bundles 
of a palm, yet their structure and arrangement are very different in the two cases. It 
was the peculiarities displayed by these two tissues that led me to seek for the true 
affinities of those plants amongst the Marattiacese, their close resemblance to which, as 
I have already mentioned, I demonstrated at the Meeting of the British Association for 
the Advancement of Science in September 1873. My friend Professor Renault 
announced that he had arrived at the same conclusion, after studying the Autun 
examples of this type, in his memoir presented to the Academy of Sciences at Paris in 
January 1874. At that time we had not exchanged our views on the subject; hence 
our united, but independent, testimonies render our joint conclusion an exceedingly 
probable one. I may observe that there is no doubt that the Autun plants corre- 
* Comptes Rendus, 26 Janvier 1874. 
