REMAINS OF STEMS OF- DOUBTFUL AFFINITY, ETC. 361 



appears to agree perfectly with that of the preceding kind, but it is sur- 

 rounded by a secondary ring of normal wood divided by medullary rays. 



Transverse sections of leaf-stalks are very commonly found in company 

 with the pieces of stem of Lyginodendron, and in such a position that the 

 unbiassed observer would at once think it probable that they belong to the 

 stems. They do in fact show exactly the same habit as the stems, the same 

 sub-epidermal plates of strengthening tissue, and a leaf-trace of two 

 symmetrical elliptical approximated bundles, which resemble minutely the 

 bundles of the first kind described above. Their transverse section is broad, 

 the upper side flat, the lower slightly convex ; there are sharply projecting 

 edges on both sides. The resemblance to certain transverse sections of 

 stalks of fern-leaves, for example to one figured by Williamson l and 

 referred to Rhachiopteris aspera, is evident. Moreover, countless fragments 

 of the laminae of this or of a very similar form are always to be found in 

 the immediate neighbourhood of the nodules, and they have on them very 

 commonly small slightly projecting winged ribs, which appear in transverse 

 section as odd, horn-shaped, entirely parenchymatous excrescences. These 

 ribs, strange to say, are found almost invariably in exactly the same form 

 on the leaf-stalks thus associated with Lyginodendron, in which they spring 

 each of them from one of the meshes of parenchyma between the hypodermal 

 Dictyoxylon-plates. Williamson himself inclines to consider that these fern- 

 leaves and leaf-stalks belong to the stems of Lyginodendron. He says 2 , 

 ' I have pointed out the existence in the Lancashire nodules of abundance of 

 small stems or petioles, to which I gave the provisional name of Edraxylon. 

 I have since succeeded in connecting these petioles with the leaflets of 

 a Pecopteris. I think it far from impossible that these may prove to belong 

 to Dictyoxylon Oldhamium, but since I have not yet succeeded in correlating 

 them with any certainty, I shall add no more respecting them at present.' 

 Strict proof can only be supplied by sections passing through the point of 

 union of the two. 



On the other hand, there is the resemblance to Cycadeae in respect of 

 the structure of the stem, which has been already pointed out. Felix espe- 

 cially has drawn attention to these relations in a preliminary communication 3 . 

 But it is not so much recent Cycadeae which this writer would compare 

 with Lyginodendron, as the partial rings in the pith of Medullosa stellata. 

 Even if the Rhachiopteridae just mentioned really belong to Lyginodendron, 

 this would be no objection to Felix's view, since, as was shown above, there 

 is no essential difference in the lamina of the leaf between Ferns and 

 Cycads ; and Osmunda, Myelopteris and Sphenopteris refracta, Gopp. warn 

 us also to be careful in employing the leaf-bundle and its structure as 

 a ground of discrimination. But still there must have been important 



1 Williamson (1), VI, t. 52, f. 6. a Williamson (1), iv, p. 403. 3 Felix (2), p. 9. 



