OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
329 
we have seen that as the rudimentary branches pass outwards through the vascular 
zone they carry along with them many of the vessels of that zone, arranged as shown 
in fig. 28. But in none of these branches thus enclosed within the primary stem do 
we see any development of nodes with their peculiar vascular arrangements or of the 
longitudinal internodal canals. Are there two sets of branches, one with and the other 
devoid of these characteristic peculiarities ? Such is very unlikely to be the case. Do 
the vascular elements of the branch of fig. 28 re-arrange themselves into the 
characteristic Calamitean form after they emerge from the parent stem ? The curious 
“ Phragmata ” existing in the closest connexion with the grooved, sandstone, medullary 
casts of the common specimens of Calamites seem to indicate the contrary, and to show 
that the peculiar conditions which occasioned the grooved contours of the medullary 
casts of the parent stem, existed equally in the branches where the latter were in close 
contact with the parent medulla. Then, again, what are the examples represented in 
figs. 8, 9, and 10 of this memoir, in which we have states whose size indicates even a 
much earlier degree of development than is seen even in the branch of fig. 28 ? In them 
the formation of the longitudinal canals clearly precedes that of the vascular struc- 
tures; a stage of growth in which they closely resemble the living Equisetum; whereas, 
in fig. 28, we have a considerable development of the vascular tissues, but, as yet, no 
canals. My own impression is that, minute as many of the examples represented by 
such figs, as 8, 9, 10, 12, and 13 are, they are young plants directly developed from 
spores ; and that in their half-embryonic state they represent temporarily the per- 
manent condition seen in the more degraded Equiseta of the present day. 
Fig. 30 is a suggestive example of a Calamite in blue shale from the Upper Coal- 
measures of the Manchester district. It is in the cabinet of Mr. Drink water, 
formerly of Manchester, but now resident in the United States of America. It is 
obviously one of those examples which some of my friends would regard as not being 
a Calamodendron, but a Calamite of the supposed Equisetaceous type of C. Cistii and 
cannceformis. 
According to my hypothesis, a is the inorganic cast of the interior of the medullary 
fistular cavity of a primary stem, and a is a similar cast, only belonging to a lateral 
branch. The former organic connexion of the two is shown by the carbonised area, f, 
which I have no doubt is a relic of the thick vascular layer with which the pith was 
originally invested. The large medullary cavity of the branch a appears as if it had not 
reached the corresponding cavity, a, of the central stem, but terminated at a'\ or fully a 
\ inch from it. If this was the case this specimen would seem to indicate that the 
characteristic Calamitean features of a fistular cavity, viz., of distinct nodes, longitudinal 
grooves and the verticils of scars marking the position of the infranodal passages, began 
to appear in very young branches, not at the medullary surface of the vascular cylinder 
of the parent stem, as the phragmata already referred to seem to suggest, but at 
some distance from that surface ; in which case the connexion between the two 
medullae, i.e., of the stem and of its branch, might be maintained by means of such 
2 u 2 
