264 DR R. KIDSTON AND PROFESSOR D. T. GWYNNE-VAUGHAN ON 
it from Professor I. BayLzy Batrour, F.R.S., it would appear that Mr Marueson only 
found one specimen of Stenomyelon, and that this had been got at Norham Bridge, — 
which the study of the anonymous paper already mentioned had led me to infer. _ 
In addition to the parts of the original specimen received from Mr Marueson by 
Professor BALFouR and Mr C. W. Pracu, in 1900 I received a few fragments attached 
to glass slips from Miss Maruxson, daughter of the original discoverer of Stenomyelon 
Tuedianum. Some additional specimens, also mounted for microscopical examination, 
were given me by Mr James Verrcn, Jedburgh, to both of whom I take this opportunity — 
of recording my sincere thanks. 
Description oF SrzwomyeLton Tvxpianum, Kipston. By R. Kinston and 
D. T. Gwynne-VauGHan. 
Owing to the imperfect preservation of the softer tissues of the specimen it is 
not possible to determine the true outline of the stem, for in all cases the thin-walled 
tissues of the cortex are completely disintegrated and destroyed. As a result, the 
stem has become flattened, and those tissues of the cortex that remain form wing-like 
projections on two opposite sides of the stele. One of these extensions is seen in its 
entirety, but of the other only a part is preserved. In some of the sections it is quite 
narrow, having a regular and very wing-like appearance (figs. 1-2), while in others 
it is much wider, and is irregularly crushed in at its margin (fig. 3). The xylem of 
the stele has not suffered any damage, and is almost circular in section. We are 
of the opinion that the present appearance of the fossil does not imply that the stem 
of the living plant actually possessed wings, but it will be shown that the leaves were 
arranged in three rows, and it is therefore quite possible that the stem possessed three 
more or less prominent decurrent ridges. 
Description of the Stem. 
The xylem mass of the stem contains both primary and secondary xylem, and as a 
whole measures 8-9 mm. in diameter. The primary xylem forms a bluntly triangular 
or three-lobed central mass, which measures 8-4 mm. from the extremity of one lobe to 
that of another (figs. 6-10). It consists of tracheze alone, except for a few occasional cells 
of parenchyma near its periphery. There are also three bands of parenchymatous tissue 
in the primary xylem which extend from the middle of the sides of the triangle so as to 
separate the three lobes more or less completely from one another. These parenchymatous 
stripes, although always quite narrow, vary somewhat in breadth, and they also form a 
few small irregular bays projecting into the tracheal masses of the lobes. Sometimes, 
but rarely, the three stripes are continuous to the centre, and then the lobes of the xylem 
are completely separate from one another. More often one or the other of them is 
interrupted by a wider or narrower bridge of trachez, so that two of the lobes are con- 
