888 PROFESSOR W. C. WILLIAMSON AND DR. VD. H. SCOTT ON THE 
present, could not have been overlooked.* The infranodal portion of the ray is per- 
sistently parenchymatous throughout the whole thickness of the secondary wood, and 
scarcely ever contains any interpolated tracheides. Hence, in tangential sections 
through the outer wood, where the principal rays generally are obliterated by inter- 
fascicular wood, the lenticular masses of parenchyma below each node form a most 
conspicuous feature (see photograph 6, also WILLIAMSON, “ Organization,” Part IX., 
Plate 20, fig. 24). Somewhat similar persistent tracts of parenchyma are sometimes 
found immediately above the node, but they are on a much smaller scale. 
It very frequently happens that the infranodal tissue of the principal rays under- 
goes disorganization of its inner cells, leading to the formation of the radial mfranodal 
canals, so fully discussed in previous memoirs.t It is well known that these infra- 
nodal canals afford the explanation of those protrusions on the medullary casts, which 
are placed immediately below the nodes, and between the furrows corresponding 
to the bundles (see the photographs in Plate 86). This explanation has been 
accepted by Count Sotms-Lavupacu,{ and indeed admits of no doubt, if, for example, 
we compare the wonderfully preserved cast figured in a former paper,§ with such a 
tangential section as that shown in our photograph 6. The agreement between the 
radiating, spoke-like rods of the cast, and the infranodal rays, as shown in the sections, 
is exact, not only as regards position, but also in size and sectional form. 
The extent to which the disorganization of the infranodal parenchyma took place 
during life may well have varied in difterent specimens. In any case it would have 
perished during fossilization much sooner than the woody tissue surrounding it, and 
this is quite enough to account for the marks on the casts. 
THE SECONDARY CoRTICAL TISSUES. 
It is extremely rare to find the cortex of the older specimens in any degree 
preserved. Except in the comparatively young stems already discussed, all the tissue 
from the cambium outwards has usually disappeared. The only instance of a really 
large corticated stem, with which we are acquainted, is that described in a former 
memoir,|| and already referred to above. 
Here the zone of cortex preserved is even broader than the wood, and measures 
24 inches in thickness. The preservation is very imperfect, but in the radial section 
(C.N. 80) it is possible to distinguish at least two zones of elongated, square-ended 
cells, with a regular radial arrangement. We cannot doubt that this tissue was of 
* As in C.N. 20n, 138*, and others, besides those photographed. 
+ Wictiamson, “ Organization,” Parts I. and IX. Asregards the true Calamitean stem (as distinguished 
from that of Calamopitus), these canals are especially well shown in C.N. 24, 91, 138*, and 1943, 
t Loe. cit., p. 312. 
§ Witiiamson, “ Organization,” Part IX., Plate 21, fig. 31. 
|| Winttamson, “ Organization,” Part TX., Plate 20, figs. 14-21. The sections are C.N. 79-87. 
