5 2 N. Bancroft. 
fact, Dr. Scott describes M. anglica as having roughly the organi¬ 
sation of a polystelic Heterangium (14, p. 433). Occasionally, 
accessory vascular strands, of concentric structure, are to be found 
in the cortex; these are interesting in comparison with the similar 
cortical bundles occurring in some recent Cycads. 
The foliar vascular supply is quite similar to, though perhaps 
less complicated than that of Sutcliffia. From the outer surfaces of 
the three stem-steles are given off large concentric bundles, each 
consisting of a central mass of mesarch primary wood, surrounded by 
secondary wood and phloem. During its outward passage, the leaf- 
trace divides repeatedly, losing its secondary tissues, and forming 
a group of small bundles each having exarch collateral structure. 
Each leaf-base of Medullosa anglica receives seventy or eighty 
vascular bundles, these being the product of the division of several 
original leaf-traces. Where the petiole becomes free from the 
stem, the vascular system consists of numerous collateral vascular 
bundles, arranged more or less in groups corresponding to the leaf- 
traces from which they were derived (Fig. 8). The orientation of 
the bundles is scattered and irregular. The whole structure is very 
like that of the petioles of some recent Cycads, the chief point of 
difference being the absence of centrifugal wood. Sometimes, 
however, even this difference does not appear to exist. Petioles of 
this kind are known under the generic name of Myeloxylon. 
