COMPARATIVE ANATOMY OF THE CYCADACEX. 443 
Cycas MEDIA, R. Br. 
Adult Plant. 
I investigated a large stem of this species, about 14 inches in 
diameter, and containing about a dozen vascular rings; the 
structure, therefore, would be in every respect much more 
advanced than in the previous specimens of Cycas which I 
had studied. 
The only special points to be noted here are: the peculiar 
structure of the girdle-leaf-trace bundles, and the large concentric 
strands in the cortex, the remaining parts of the structure being 
sufficiently normal. 
In the outer part of the cortex there is a very thick formation 
of periderm, consisting of but a small quantity of cork, but a 
very large amount of phelloderm, the latter containing great 
numbers of stone-cells. 
Running obliquely out from the periderm in a tangential 
direction are the girdle-leaf-trace bundles, with their xylem 
directed inwards. As seen in transverse section, i.e. in a 
radial section of the cortex, these bundles are elongated radially 
and are rather uarrow tangentially. They present a peculiar 
feature which has not been noticed in the girdles before either 
of this or any other genus, inasmuch as they exhibit a distinct 
tendency to assume a concentric structure, a cambium extending 
round in circular form on either side of the bundle and forming 
several layers of parenchyma, amongst which occar, either in small 
groups or singly, isodiametric or slightly elongated, reticulate 
tracheides, of very irreguiar, angular shape. In some bundles 
the concentric disposition of these secundary cells is not so 
obvious, but in others they form a nearly complete circular 
strand, of which the bundle is a segment. As seen in longitudinal 
section of the bundle, the xylem of its main part consists, on the 
inner side, of a band of reticulate elements, which are succeeded 
by scalariform tracheides, next to these come tracheides with 
Very thick walls, and, apparently, simple pits, for no border is seen 
to be developed; the tracheides nearest the phloem have very 
larrow, elongated, bordered or scalariform pits. These girdles 
ave an irregular course, and there occur, moreover, between 
them curved radial connexions. 
In some parts of the cortex, at its extreme outer edge, and 
