372 HICK AND CASH: FOSSIL FLOEA OF HALIFAX. 
The Cortex — Outside the cambium zone is the Cortex, which 
for descriptive purposes may be regarded as consisting of three 
portions. 
1. The inner Cortical layer (PI. 1, i.e.) — This layer hardly seems 
to be quite continuous round the stem, but this is obviously due to 
slight imperfections in the specimen. In those parts where it is 
best preserved, its appearrance strongly resembles that of the trans- 
verse section of the xylem of a fern, presenting a central series- of 
large thick-walled elements (vessels ?), enclosed both on the outside 
and on the inside by one or two rows of smaller but similar thick- 
walled elements. At one or two points this layer seems to dip 
down through the cambium zone to the vascular zone, and thus 
divide the cambium into separate and distinct portions. The specimen 
does not show whether such a dipping down obtained all round the 
stem, and this point is not determinable by our other sections. As 
the dippings down that are present are opposite the intervals between 
the vascular bundles, the portions of the cambium they enclose are 
opposite the bundles themselves. If other specimens should enable 
it to be demonstrated that such an arrangement is characteristic of 
Calamites, the different portions of the inner cortex would occupy 
the same positions with respect to the vascular bundles, as the phloem 
masses of Dicotyledonous stems, and might be homologous with them. 
Some of the large elements of this layer, contain a black car- 
bonaceous mass, and others a complete or incomplete ring of similar 
material. Whether this is to be regarded as the fossilised represen- 
tative of ^resinous, protoplasmic or other substances which these 
elements contained we cannot venture to say. 
2. The middle Cortical layer. (PI. 1, m.c.) — This consists of 
thin-walled tissue with a peculiar arrangement. The cells of which 
it appears to be chiefly composed, are grouped into radial masses, 
which broaden towards the periphery, something like the medullary 
rays of Tilia. Between these struts of cells, there are larger or 
* The term Cortex is here used provisionally for the whole of the tissues 
that lie outside the Cambium, which produces the successive layers of Vascalar 
Tissue. This is not strictly in accordance with the practise of botanists in des- 
cribing recent plants, but the term seems much more appropriate than Bark, by 
which these tissues of fossil plants are frequently designated. 
