Monthly Microscopican 
Journal, Aug. 1, 1869. J 
some Exogenous Stems. 
67 
transverse sections of wliicli exliibit a structure identical with that 
of Hving conifers ; but longitudinal sections show that the vessels 
or fibres are altogether different from the glandular or discigerous 
type. Instead of bearing rows of discs, and only on the surfaces of 
the vessels parallel with the medullary rays, their entire walls are 
covered with reticulations formed by the deposition of lignine in the 
interior of the vessels. All the specimens which have been latterly 
collected have been of this character ; hence some of the most 
experienced phytologists came to the double conclusion that whilst 
the plants in question were true Dadoxylons, both Endlicher and 
myself had mistaken the internal reticulations of the fibres for the 
lenticular discs of true glandular fibre. Had this explanation been 
correct, we should have been left without any true coniferous wood 
in the Coal-measures. But it is not correct, as I shall now proceed 
to demonstrate. 
Fig. 1 represents two fibres from my now celebrated specimen 
from Coalbrook Dale. The surfaces shown are those parallel to the 
medullary rays, and it will be seen that these surfaces are entirely 
covered in every fibre with discoid areolations. In some instances 
(Fig. 1, a) there are two vertical rows of these areolae : the mutual 
pressure of their inner contiguous margins of which gives them 
a somewhat hexagonal form ; but in other examples, as at Fig. 1, a, 
there is a distinct interval between the discs. In Fig. 1, 6, we have 
three such vertical rows : the centre row, especially, having the 
hexagonal form to which M. Brongniart refers in his description of 
Dadoxylon. The only point in which these structures difier from 
the similar ones of living Araucarian conifers is the absence of the 
central dot in each disc. Of this I have never been able to detect a 
trace. 
Fig. 2 represents two similar fibres as they appear in a tan- 
gential section of the stem. The surfaces (2, a) are here entirely 
smooth, being free alike from discs and reticulations. But between 
the contiguous fibres (2, h) we have a headed structure revealing the 
discs of Fig. 1, seen in section. The fibre-walls (Fig. 2, c) are very 
distinct, and afibrd the clearest proof that the discs are external to 
the fibre, as in recent conifers. There cannot be the slightest room 
for doubting that, whether the fructification of the tree was or was 
not coniferous, we have here a modification of true glandular or 
discigerous pleurenchyma. But if we turn to the more abundant 
examples of the so-called Dadoxylons, we shaU find an altogether 
different structure. 
Fig. 3 represents a fibre of the plant which Mr. Binney has 
designated Dadoxylon Oldhamium, and which, in the specimen 
figured, exhibits* the most magnificent instance of reticulated 
* This specimen is from the rich cabinet of Mr. Butterworth, of High Cromp- 
ton, near Oldham. 
F 2 
