222 Weiss . — A Stigmciria with Centripetal Wood. 
character and the morphology of the Stigmarian axis, it seems desirable 
to describe in some detail a specimen which has come into my possession 
through Mr. James Lomax, of Bolton. 
It was found in a calcareous nodule from the well-known Hard Beds of 
Halifax, and is of small size, the central vascular cylinder measuring only 
•75 cm. in diameter. Dr. Scott, to whom I showed the specimen, drew my 
attention to the resemblance of its primary wood to that of the stem of 
Lepidodendron mundum , and particularly of the axis as a whole to that 
figured by Williamson (’ 89 ) as a stem of Lepidodendron mimdnm with 
secondary thickening. An examination of this specimen in the Williamson 
collection at the British Museum convinced me that we had to do with the 
same plant as that described by Williamson, and the account which follows 
will, I think, suffice to show that in it we have a true Stigmarian axis. 
Whether or not it is to be associated with the stem showing the structure 
of Lepidodendron mundum 1 will remain for subsequent discussion. It is 
interesting to note that the specimen described by Williamson (cabinet 
number 416 b.) comes from the same locality as the one before us, and the 
agreement with our specimen is so close that I was at first inclined to 
believe that they must have been cut from the same block, but Mr. Lomax 
assures me that the nodule from which the second specimen was cut was 
quite untouched when he commenced to work on it. How many sections 
the first nodule yielded it is impossible to say, but one preparation in the 
Cash Collection, now in the University of Manchester, is obviously from 
the same block, and is also labelled Lepidodendron mundum. (Cash 
Collection, Q. 403 A.) 
It should also be mentioned that there are in Dr. Scott’s collection 
several slides of an axis, slightly larger but somewhat compressed, which 
appear to be sections of a similar plant (Nos. 1815 and 1825). 
The vascular axis of the recently discovered specimen is about the same 
size as Williamson’s specimen ; and seen in transverse section might well 
be mistaken for a Lepidodendron twig. Of the outer tissues the periderm 
alone is preserved, and is arranged in wide folds around the vascular cylin- 
der (see Fig. 1, PI. XV). In its greatest extension it measures 4 cm., but 
this does not give a real idea of its size, as one of its folds comes right in to 
the central cylinder. As near as possible the periderm must have had a 
circumference of not less than 15 cm., while that of the central cylinder is 
about 2 cm. 
Th z periderm consists of 6-8 rows of thin-walled rectangular cells, and is 
very similar to that of a typical Stigmaria , such as S.ficoides. It shows a 
considerable tangential extension of many of the external rows of cells, which 
has been recognized as a characteristic of the Stigmarian bark. (See Scott, 
1 According to Mr. James Lomax the stem showing internally the structure of Lepidodendron 
mundum had externally the marking of Bothrodendron. 
