1047 
Affinities of Sutcliffia. 
or, the apparent ‘ middle lamella ’ may represent the whole thickness of the 
wall, the thick-walled appearance being delusive and depending on some 
change in the cell contents. In the new stem the ‘ middle lamella 5 usually 
appears to be quite distinct from the remainder of the apparent c thick wall ’, 
so that Scott’s second suggestion would certainly appear the more probable 
explanation in this case. In longitudinal section the phloem is seen to be 
composed of strands of long, narrow, tapering elements (PI. XCI, Fig. 4), 
and the short-celled parenchyma of the medullary rays ; in the latter 
secretory elements frequently occur. 
Immediately beyond the phloem lies a somewhat narrow zone of very 
badly preserved tissue containing numerous large, secretory sacs ; this 
tissue appears to be sharply marked off from the cortex and may possibly 
represent the pericycle. 
3. Structure of the Leaf-trace Bundles . The number of leaf-trace 
strands occurring in the series is extraordinarily small, and it is evident, con- 
sidering the length of stem under examination, that the leaves could only 
have occurred at long intervals. It is known that some of the Permian 
Medulloseae were fair-sized trees, 1 and doubtless Stitcliffia should be in- 
cluded among them, though it is just possible that the suggestion put 
forward by Goppert and Stenzel 2 that some members of the family were 
climbers may apply here, but much more evidence needs to be brought 
forward before any definite statement can be given. 
Where leaf-trace strands occur in the series they are always in clusters 
of two or three closely associated together, giving further weight to the 
suggestion that their derivation is by the breaking up of a ‘ meristele ’ ; the 
only exception is the isolated trace derived from y, but this is probably to be 
regarded as a premature phenomenon and not as a normal feature. In one 
case two adjacent, distinct leaf-traces appeared to be approaching prepara- 
tory to fusion, but whether this actually occurred cannot be stated, for the 
leaf-traces disappeared from the series before the critical region was reached. 
As in Sutcliffia insignis , two types of foliar bundles exist ; the larger have 
several protoxylem groups distributed around the wood, and are thus 
radially symmetrical ; the smaller have either one or a twin protoxylem group 
and are unilateral ; in both cases the wood is exarch (Text-figs. 3, 14, and 1 5). 
The zone of ground tissue is too narrow to determine whether the 
radially symmetrical strands bifurcate during their outward passage, pro- 
ducing unilateral foliar bundles ; from the fact that in S. insignis 3 the 
former occurred near the ‘ meristele ’ zone, and the latter in the leaf-base, it 
is probable that this takes place. 
In both types of bundle the tracheides are mixed with parenchyma as 
1 Scott, D. H. : Studies in Fossil Botany, 2nd ed., Part II, p. 443. 
2 Goppert und Stenzel : Die Medulloseae, eine neue Gruppe der fossilen Cycadeen. Palaeonto- 
graphica, 1881. 3 Scott : S. insignis , loc. cit., p. 57. 
