254 de Frame . — On Medullosa cenlrofilis, a New Species of 
In Medullosa anglica 1 the leaf-bases also appeared to clothe completely the 
stem surface ; there also they were decurrent and confluent with the stem 
for a great vertical distance, at least 13 cm., so that in these respects the 
two plants show great similarity. 
In M. anglica , Scott was able to determine the arrangement of the 
leaves, but in the present specimen this could not be definitely ascertained, 
but the phyllotaxis certainly does not appear to be consistent with that of 
M . anglica , where the divergence has been shown to be two-fifths. 
The vascular tissues of the stem are entirely enclosed in a narrow zone 
of tissue pd ., which represents the beginning of periderm 2 development 
(Text-fig. 1). The vascular system consists of an outer ring of four steles, 
reduced by fusion to three in the upper part of the specimen, enclosing 
a central stele or star-ring (6, Text-fig. 1). The greatest interest of the 
specimen lies in the presence of this star-ring, for hitherto such a structure 
has not been described in any of the Medulloseae of Lower Coal Measure 
age, although the Permian members of the genus Medullosa are all 
characterized by the occurrence of such strands. 3 
The structure of the steles is essentially similar in every case. The 
central portion of each is composed of a mass of primary tracheides inter- 
mixed with parenchyma ; surrounding the primary xylem is a zone of 
secondary wood of variable thickness ; but no phloem is preserved round 
any of the steles. 
III. The Steles. 
The size of the individual steles varies considerably, as the maximum 
dimensions of transverse sections taken from the uppermost slide, A, will 
show : 
Stele a 4-5 mm. X 3 mm. 
,, (3 7 mm. x 4 mm. 
,, y 9 mm. x 5 mm. 
,, b 2 mm. x 1*5 mm. (star-ring). 
. 
The form of the stele is somewhat irregular and varies in the course of the 
series; but the star-ring remains consistently oval throughout (cf. PI. I, 
Fig. 1 and Fig. 2). 
The whole of the interior of the steles is occupied by a mass of 
primary wood associated with thin-walled parenchymatous elements ; the 
structure is strikingly similar to that of one of the steles of Medullosa 
anglica, except that there appears to be less variability between the pro- 
1 M. anglica , loc. cit. 
2 Scott describes an internal periderm surrounding the steles in Medullosa pusilla, p. 222. 
3 Weber, O., und Sterzel, J. T. : Beitrage zur Kenn-tniss der Medulloseae. Ber. der Naturw. 
Ges. zu Chemnitz, vol. xiii, 1896. 
