1056 de Frame. — On the Structure and 
because the description given by him appears to explain in a satisfactory 
manner the way in which the similar strands in Sutcliffia may possibly have 
arisen from parenchyma cells. It is, however, impossible to state the mode 
of origin with certainty, as no stages between the clusters of tracheides 
formed from cortical or pericyclic cells and fully formed arcs or strands 
were observed. 
The investigations of Weber and Sterzel 1 have shown that in Medidlosa 
stellata , var. gigantea , and probably also in M. Solmsii , var. lignosa , extra- 
fascicular zones of vascular tissue occurred outside the system of steles, and 
that these zones were very similar to those found in Cycads of the present 
day. Scott 2 also found that in Medidlosa anglica irregular bands may 
occur in the stem which are ‘ probably best regarded as extrafascicular new 
formations, comparable to . . . the irregular strands which sometimes occur 
in the extrafascicular region of Macrozamia \ 
There still remains one further structure of interest to be described, a 
strand which appears in a few sections only, and which lies beyond the other 
vascular tissues. It consists of a concentric bundle of fair size, the maximum 
diameter being about 2 mm., the whole being slightly elongated tangentially 
(PI. XCII, Fig. 6). Short isodiametric tracheides with reticulate markings 
form the bulk of the central region of the strand (PI. XCII, Fig. 7), and 
round them lies a zone of secondary wood, completely encircled by secondary 
phloem ; the structure of the latter appears precisely similar to that 
surrounding the stele and c meristeles ’. All the wood elements are smaller 
than those of the extrafascicular strands : the average diameter of the 
secondary tracheides only reaches 33-3 \ a, whereas in the former they are 
usually 1 1 5-8 /x . The short tracheides have a diameter nearly twice as 
great as the elements of the secondary wood, and are 58.3 /x broad. 
The resemblance of this strand of the accessory vascular strands of 
Medidlosa anglica is very striking. Scott instituted a comparison between 
these latter and the cortical bundles of Cycas , and states that he regards 
them, as also the extrafascicular bands, as ‘ characteristic Cycadean 
anomalies ’, which comparison and interpretation might well be extended to 
Sutcliffia also. 3 
VII. Attribution of the Specimen. 
The fossil stem here described has been attributed to the genus Sutcliffia 
on account of the close resemblance it exhibits to the only other stem of 
the genus at present known, viz. Sutcliffia insignis. The general structure 
of the vascular system is identical in the two fossils, for both have a simple 
1 Weber und Sterzel : Beitrage zur Kenntnis der Medulloseae, p. 116, and Taf. viii, Fig. 2. 
2 Scott, Medidlosa anglica : loc. cit., p. 98. 
3 Compare Scott, Medullosa anglica , loc. cit., p. 98, PI. XII, Fig. 18, with PI. XCII, Fig. 6 of this 
paper and with Worsdell, loc. cit., 1898, Figs. 6-8, 1896, Figs. 2, 9, and 10. 
