OF THE FOSSIL PLANTS OF THE CO*AL-MEASTTKES. 
499 
of these conclusions. Plate XXVIII. fig. 37 represents part of a longitudinal section of 
the specimen of Calamojntus, of which figs. 19 to 25 inclusive exhibit other aspects. 
Like figs. 23 & 24 it is a vertical section which has traversed one of the horizontal por- 
tions (37 c) into which each longitudinal canal, in that variety, divides at the node : we 
have the usual arched nodal arrangement of the wood-vessels ; and at m is indicated the 
position of a branch of which the tissues have perished, such a branch being identical 
with those indicated in Plate XXVI. fig. 25 m, at the lower extremity of the primary: 
medullary ray V in fig. 22, in Plate XXIV. fig. 13, and in Plate XXIII. fig. 2 m. In 
all these examples, except 25, we find evidence not only that the branches originate in 
the innermost part of the woody zone, receiving additional vessels from the latter as they 
proceed outwards, but in several of them we have proof that a minute amount of cellular 
tissue in their centre forms a pith, continuous with that of the parent stem, as I have 
already shown to be the case with the larger subterranean branches. In the Ccdamopitus 
already so often referred to this is very marked. In the section delineated in plate 4. 
fig. 15 of the memoir quoted, and reproduced at Plate XXVIII. fig. 38 of this memoir, 
we see that this cellular tissue already appears as a well-defined pith. But since the 
above description was written, Mr. Lutterworth has placed in my hands a transverse 
section of a stem which has been about an inch in diameter without its bark. The 
section has taken a slightly oblique direction, one half of it passing through the node, 
and the other a little on one side of it. But fortunately the nodal portion passes through 
the finest example of an aerial branch I have yet seen, and which accords with the 
remarks already made. Plate XXVIII. fig. 39 represents the branched part of the 
section referred to. The plant has belonged to the same type as fig. 16, not being 
furnished with longitudinal canals*. The base of the branch (m), and which is inserted 
into the woody zone, is wedge-shaped. It takes its rise from the innermost or medullary 
angle of one of the woody wedges, the two halves of which are pushed asunder 
by it as it proceeds outwards, receiving additional vessels from each half as it does so, 
increasing its diameter. At its medullary extremity its vessels are distinctly seen to be 
intermingled with some large cells, reminding us somewhat of the arrangement seen in 
fig. 3 ; but the chief portion of the branch consists of parallel vessels which pass 
directly outwards. I conclude that the section has cut through the branch a little on 
one side of its medullary portion, which consequently is not seen. The part imbedded in 
the woody zone, as well as the remaining portion of what has been external to it, con- 
sists of one undivided joint or internode, no transverse nodal constrictions being visible 
in it. At its emergence from the woody zone the branch has a diameter of T01 of an 
inch, which is about one half more than that of the exteriors of the woody wedges in its 
neighbourhood. The wedge from which it springs is thus dilated by it at that point to 
about double its usual dimensions. These measurements sustain what I have already 
said respecting the small size of the aerial branches. We thus have the longitudinal 
transverse and tangential sections of Calamites combining to fix with approximate cer- 
tainty the position of these branches in relation to the central axis. These conclusions 
* See note on p. 488. 
