417 
Scott . — On Peduncle of Cycadaceae . 
especially the latter, are essentially monostelic, Heterangium 
directly connecting Lyginodendron with the type of stem- 
structure now represented by Gleichenia , & c. 
Recent Cycads and, so far as I am aware, the Mesozoic 
Bennettiteae also, have evidently monostelic stems, and the 
observations recorded above tend to connect them with the 
Lyginodendreae rather than with the other intermediate 
groups. On this point, however, it is necessary to speak 
with great caution, for the distinction between polystely 
and monostely — so striking in the extreme forms — is one 
on which it is quite possible to lay too great stress 1 . We 
may, however, safely go as far as this : the discovery of 
mesarch bundles in certain axial organs of Cycadaceae, 
establishes a new link between that family and the Lygino- 
dendreae, though by no means excluding the possibility of 
relationship in other directions. 
The other point of interest recorded above, is the occasional 
occurrence of concentric vascular bundles in the cortex of the 
peduncle. This is a very inconstant phenomenon, and 
I hesitate to attach great importance to it, for we know 
that concentric structure sometimes appears in the foliar 
bundles of various Angiosperms, where there can be no 
question of phylogenetic significance 2 . 
The cortical bundles of the peduncle in Stangeria appear 
to represent a vestigial leaf-trace system, no longer connected 
with leaves. It is possible that a primitive structure has 
sometimes been retained by these now rudimentary strands. 
The concentric structure suggests a comparison with Medul- 
loseae, but a better analogy can be found among the 
Lyginodendreae, for the leaf-traces in the cortex of Calcimo- 
pitys Saturni appear to have been perfectly concentric 3 . In 
Lyginodendron the leaf-traces were collateral, only becoming 
concentric in the leaf itself. 
1 On this point see, for example, Mr. Gwynne-Vaughan’s paper on Polystely in 
the genus Primula , Annals of Botany, June, 1897. 
2 Cf. Gwynne- Vaughan, loc. cit. 
3 Solms-Laubach, Pflanzenreste des Unterculm, Plate IV, Fig. 11. 
