1058 
de Fr aine. — On the Structure and 
extremely probable that the presence of the secondary tissues and the 
extrafascicular strands may be explained on the same grounds, for in 
S. insignis slight secondary growth had taken place around the stele and 
‘ meristeles ’ in the lower parts of the specimen, and the resulting tracheides 
agree absolutely with those in the new stem. 
The apparent absence of secretory elements from the xylem parenchyma 
constitutes the most serious difficulty in assigning the fossil to Sutcliffia 
insignis, but in one ‘ meristele ’ such elements can be readily detected 
(Text-fig. 10), and, moreover, it appears very probable that under more 
favourable preservation similar elements would be found generally dis- 
tributed among the primary tracheides (see p. 1044). 
Until further evidence is available it would appear desirable, therefore, 
to attribute, provisionally, the new specimen to Sutcliffia insignis ; on this 
view Scott’s specimen would be the stem in its young state, whereas the 
present fossil would show the complexity 1 attained in the older, though 
smaller, plant. 
VIII. Affinities. 
In the original description of the genus, Sutcliffia 2 is included in the 
family Medulloseae, and as the reasons for this conclusion are so fully stated 
there, it is quite unnecessary to add further remarks on this question. The 
additional data afforded by the new specimen only serve to bring into still 
closer relationship the two genera, Sutcliffia and Medullosa, through some 
such forms as Medullosa anglica, the simplest and geologically oldest known 
member of its genus. 3 The protostele of Sutcliffia, with its wide zone of 
secondary tissues, bears a very close resemblance to one of the three steles 
of M. anglica, the main difference depending upon the mesarch nature of 
the protoxylem in the latter species compared with its universally exarch 
structure in the former. Extrafascicular strands of wood and bast and 
accessory vascular bundles are present in both ; and finally there appears 
to be no serious objection to the view that the c meristeles * of Sutcliffia are 
homologous with the leaf-trace strands which leave the stele in M. anglica, 
for both appear to be entirely used up in the formation of foliar bundles. 
It remains to be considered whether the new specimen throws any 
further light on the affinities of the Medulloseae with other groups. Scott 
expressed the view that Sutcliffia is * the most primitive member of the 
Medulloseae yet discovered ’, though he continues, ‘ it is doubtful, however, 
whether it lay on the direct line of descent of any of the more complex types 
with which we are acquainted.’ He considered that its structure £ has not 
advanced very far beyond the simple protostelic condition ’ of such a form 
1 Cf. Scott, Sutcliffia insignis : loc. cit, p. 54. 2 Scott, Sutcliffia insignis : loc. cit., pp. 63-5. 
3 Scott, Medullosa anglica : loc. cit., pp. 114-15. Studies in Fossil Botany, Part II, 1909, 
p. 428. 
