262 de Fr aine. — On Medullosa centro fills, a New Species of 
with three adherent leaf-bases, but four are present in the new specimen. 
A more important feature is the absence of any secondary tissues accom- 
panying the leaf-trace on its passage from the stele into the cortex, a 
peculiarity which the specimen appears to share with M. pusilla. 
The most distinctive character, however, is the organization of the stem 
steles into an outer ring of three or four steles, enclosing a central strand or 
star-ring : it is chiefly on account of this feature — a feature which may be 
considered as a foreshadowing of the structures so characteristic of the 
Permian members of the genus — that the specimen has been distinguished 
by a specific name ; 1 at the same time there can be no doubt that the three 
species are very closely related. 
In an account of the genus Medidlosa by Weber and Sterzel, 2 the then 
known specimens of the genus were arranged in groups or form-cycles. 
Each form-cycle consisted of a typical species and included those specimens 
which were either varieties of the type or species closely related to it. Up to 
1896 four of these form-cycles were recognized — namely those of Medullosa 
stellata , Cotta ; M. porosa , Cotta ; M. Solmsii , Schenk ; and M. Leuckarti , 
Gopp. & Stenz. ; the species of the genus provided by the English Coal 
Measures would appear to furnish a fifth, with M. anglica , Scott, as the type 
and the new specimen and M. pusilla 3 as closely allied species. 
It has already been pointed out by Scott 4 that M. anglica approaches 
most closely to M. Leuckarti among the Permian Medulloseae, not only on 
account of the structure of the individual steles, but also because of the 
close agreement in leaf characters ; moreover, M. anglica , M. pusilla , and 
M. Leuckarti appear to be the only hitherto described species in which 
secretory canals occur. 5 Finally, it is of interest to note in this connexion 
that the number of star-rings may be very few in M. Leuckarti ; indeed, the 
specimen figured by Weber and Sterzel 6 with three peripheral sinuous 
steles enclosing five ‘ Sternringe * offers a striking comparison with the new 
specimen. 
In conclusion, I am glad to take this opportunity to express my 
gratitude to Professor F. W. Oliver, in whose laboratory at University 
College, London, this investigation was carried out, not only for handing 
over the slides to me for description, but also for the advice he has given 
me during the course of the work. 
1 If the protoxylem of the steles should prove to be exarch, this would provide a further feature 
distinguishing the stem from M. anglica . 
2 Loc. cit. 
3 Scott: M. pusilla , loc. cit. 4 Scott : M. anglica , loc. cit., p. 114-5. 
5 Bancroft, N. : III. Rhexoxylon africanum , a new Medullosean Stem. Trans. Linn. Soc., 
Lond., Ser. 2, Bot., vol. viii, Pt. 2, 1913. 
6 Loc. cit., Tafel V, Fig. 2. 
