OE THE EOSSIL PLANTS OE THE COAL-MEASUEES. 
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"branches and twigs an abundance of precisely similar bundles ; but in these plants they 
are single, not in pairs. They are unmistakably the leaf-bundles of the Araucarioe ; 
and I have no doubt that such is also the character of those in the fossil branches. 
Their greater number in the small branches than in the larger and more fully grown ones, 
their invariable origin from the innermost surface of the ligneous cylinder, and their 
apparent disappearance in the peripheral portions of the larger branches, are all facts 
which point in the same direction. But why are these bundles arranged symmetrically 
in pairs 1 Either two bundles went to one leaf with a double midrib, or the leaves were 
arranged in pairs, either of which conditions may prove a possible means of identifying 
these stems with their foliage, not to be lost sight of by those who are working amongst 
the plant-impressions of the Coal-measures. 
Eig. 50 is part of a radial section of a fragment of the ligneous cylinder of a Dadoxylon 
from Binns Clitf, in Burntisland, Fifeshire, for which I am indebted to my friend Mr. 
Grieve. Fig. 51 is the lateral surface of one of its fibres. Its structure differs in no 
material respect from those already described. The disks are sometimes in two rows, 
sometimes in three, as represented in fig. 51. Though coming from so much lower a 
geological horizon than those described in the preceding pages, I can detect no material 
difference between it and the Dadoxylons from the beds above the Millstone Grit. 
Fig. 52 is a portion of another fibre from a fragment from near Oldham. In it each 
of the disks shows a vertical central line, partly crossed by an oblique one coming from 
above downwards, but which' becomes very indistinct after it has reached the more 
distinct vertical one. This is the only example I have met with from the Oldham 
deposits in which a trace of the central spot so universal in the bordered disks of living 
Conifers is to be seen. 
These facts appear to me to justify the conclusion that the specimens described really 
belonged to Gymnospermous plants allied to the Coniferse. On comparing the sections 
of the Coalbrookdale specimen (figs. 33 & 36) with several recent forms we see at a 
glance how close is the resemblance between them. Thus, on examining a longitudinal 
section of a young branch of Taxus, we obtain an exact copy of fig. 36, the portion d 
being the liber, with its vasa propria and longitudinal resin-canals, whilst the parenchyma 
(i e ) is a phelloderm layer, the cells of which, in the recent stem, are full of chlorophyl 
grains. Young shoots of Araucaria braziliensis present similar resemblances. The 
bark of my fossil exhibits no development of the phellem layer seen in Salisburia adi- 
antifolia and similar stems. The other tissues equally display characteristic resemblances. 
Thus the medulla is encased in a medullary sheath (fig. 35, b'), and this in turn is invested 
by a xylem layer composed of thick-walled prosenchyma, without any admixture of true 
vascular elements. Added to this we have the orientation of the leaf-bundles ; and, 
finally, the fine fragment, in my cabinet, figured in my memoir in the ‘ Monthly Micro- 
scopic Journal’ for Aug. 1869, plate xx. fig. 7, exhibits a thick branch passing straight 
through the wood of the stem, the layers of which latter surrounding the “ knot ” are 
thrown into undulating folds, exactly as would be the case with a piece of pine-wood that 
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