Notes . 
185 
wood consists of radial series of tracheides and medullary rays ; the 
secondary tracheides bear multiseriate bordered pits on their radial 
walls ; most of the primary tracheides are pitted in the same way, but 
on all sides alike. In the neighbourhood of the protoxylem-groups 
the tracheides of the primary wood are spiral or scalariform. The 
phloem is made up of elongated elements, presumably the sieve-tubes, 
forming a net-work, the meshes of which are occupied by the phloem- 
rays. 
Each stele of Medullosa anglica shows the closest agreement in 
structure with the single stele of a Heterangium , so that the stem of 
this Medullosa might well be concisely described as a polystelic 
Heterangium. 
The course of the leaf-trace bundles was followed very completely 
in consecutive series of transverse, and in longitudinal, sections. The 
leaf-traces leave the steles precisely in the same manner as in Heter- 
angium. On becoming free the trace is a large concentric bundle, 
surrounded by its own zone of secondary wood and bast. As it 
passes obliquely upwards through the cortex, the trace loses its 
secondary tissues, and undergoes repeated division into a number of 
smaller bundles, each of which has collateral structure. These col- 
lateral strands have in all respects the same arrangement of their 
elements as the well-known bundles of Myeloxylon. 
The base of the leaf received a large number of bundles, consisting 
of the ultimate branches derived from the subdivision of several of the 
original leaf-traces. This distribution of the bundles is peculiar and 
unlike that in any known plants of Cycadean affinities. 
In a few cases accessory vascular strands, of concentric structure, 
recalling the cortical bundles of a Cycas, were found to the outside of 
the normal stelar system. 
The stem formed a well marked zone of internal periderm. In one 
specimen the whole of the outer cortex, with the leaf- bases, had been 
exfoliated, so that in this case the periderm formed the external 
surface. 
The leaf-bases and petioles present in all respects, as regards 
hypoderma, vascular bundles, and gum-canals, the characters of the 
Myeloxylon Landriotii of Renault, which was evidently not a species, 
but a type of leaf-stalk common to various Medulloseae. The petioles 
branched repeatedly, the finest ramifications of the rachis having a 
diameter of about 1 mm. only, but retaining in essentials the ‘ Myelo- 
