OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
figs. 8, 10, and 13 is a primitive generalized parenchyma; but as the stems became 
arborescent, this genera liz ed tissue developed within its interior the thick layer of 
prosenchyma which resembles so closely the cork layer of living Phanerogams. It will 
be remembered, however, that we find the same kind of tissue, in an almost identical 
position, in Lepidodendron Harcourtii as well as in all other Lepidodendroid and 
Sigillarian stems. 
In my first memoir of this series (Phil. Trans., 1871, Plate 26, fig. 26 ; Plate 27, 
fig. 33, and Plate 28, fig. 38), I illustrated the general arrangement of the tissues at 
the node of the young Calamite. Since that memoir was published I have obtained 
some additional examples throwing light upon those curious structures. Plate 26, 
fig. 25, of that memoir represents a similar section to figs. 23 and 24 of the present 
one. In all these sections we see each of the vascular wedges of one internode 
(within which internode it is separated from its neighbours by the cellular primary 
medullary rays) subdivided into two portions, the half of one wedge uniting with the 
contiguous half of its next neighbour to form a new wedge hi the next internode, 
whether above or below. I pointed out the existence at and near each node of two 
very distinct verticils, of objects. One of these verticils, situated immediately upon 
the node, appeared to me to represent bundles of specialised tissues going off to supply 
verticils of organs, probably small twigs or leaves. The second verticil instead of 
being planted upon the node occupied the uppermost portion of each internode. I 
showed that, in three distinct specimens, there existed at the uppermost extremity of 
each primary medullary ray a peculiar cylindrical or laterally compressed canal, from 
which all tissues had disappeared, and which was filled with the same inorganic 
material as that which occupied the fistular cavity of the pith. These passages I 
designated the infranodal canals. I further demonstrated, in fig. 22 and p. 490-91, 
that the areas which these canals occupied were originally filled with the cells of the 
primary medullary rays through which the canals subsequently passed. These cells 
became first ruptured, and secondly absorbed, leaving behind a verticil of sharply- 
defined canals arranged in a regular radiating order and passing to the periphery 
of the vascular zone. Some sections of a Calamite, for which I am indebted to 
Mr. Bitttebvvorth, exhibit these organs under a somewhat new aspect. In fig. 23 we 
have the vascular wedges at f and the primary medullary rays at c, c , c", the former 
exhibiting the nodal bifurcations to which I have just referred. We here see that 
at the nodal extremity, l, of each medullary ray of the lower internode, c , c , there is 
a small mass of cells of much smaller size than those which constitute the rest of the 
ray. These special cells occupy the centre of a lenticular enlargement of the end of 
the ray. It will also be observed that the lower extremity of each of the rays, c", c", 
of the upper internode the ray communicates by a very narrow neck with a small 
lenticular cellular organ, to, the central cells of which again are much smaller than 
those of its periphery. There is no question whatever that the small cells, l, l, of the 
lower row of rays occupy the exact position of my infranodal canals, whilst those 
