426 A rber. — On the Roots of Medullosa anglica. 
There is unfortunately no record of the locality from which 
the fossil was obtained. Mr. Lomax, however, who has 
recently made several excellent sections of the stem and the 
roots, tells me he is certain, from the appearance and preserva- 
tion of the material, that it was originally obtained from the 
Lower Coal Measures of Hough Hill Colliery, Stalybridge, 
Lancashire ; the same locality and horizon as the type 
specimens. 
The examination of the structure of the stem, which in the 
Cambridge specimen is unfortunately incomplete, has added 
nothing of importance, with one exception, to the very com- 
plete account already given by Dr. Scott ; which was founded 
on a study of several different specimens. 
In association with the stem, and in one case in continuity 
with it, several exceptionally well-preserved roots occur. 
These agree very closely in structure with the roots pre- 
viously figured 1 , and they undoubtedly belong to Medullosa 
anglica . Some of these are the best-preserved specimens 
which have yet been found, for the more delicate tissues, 
especially the phloem, are almost perfect. 
A photograph of a transverse section of one of these roots 
is shown on PI. XX, Fig. 1 (compare also Fig. 6). The 
diameter is about 9 mm. The root is triarch, as are all the 
other roots of Medullosa which I have examined. The ex- 
ternal tissue consists of a somewhat narrow but well-marked 
zone of radially seriate elements, the periderm ( pd ’.). As 
Dr. Scott 2 has pointed out, this periderm is developed centri- 
petally from a phellogen (see Fig. f i^ph.gl) which lies on the 
inner side of this zone. It was also shown that this peri- 
derm is of deep-seated origin, arising, probably, in the 
pericycle 3 . 
Internal to the periderm, there is a somewhat broader zone 
of thin-walled tissue (sr), with here and there very conspicuous 
cells, or groups of cells, with dark-coloured contents. This 
1 Scott, loc. cit., PI. VIII, photos 19-25 ; PI. XII, Fig. 19 ; PI. XIII, Figs. 20-4. 
2 Scott, loc. cit., p. 102, PI. Vlil, photo 21. 
3 Scott, loc. cit., p. 104, PI. XII, Fig. 19. 
