346 ON LEPIDODENDRON AND CALAMITES. 
Lepidodendron. Mr. Binney is at present engaged in preparing an ac- 
count of its internal structure, with copious illustrations, which will be 
more complete than any hitherto published, because of the abundance 
of well-preserved specimens contained in his cabinet, the result of so 
many years’ devotion to the study of the fossils of the coal measures. 
I shall therefore content myself with a hasty sketch of the genus. The 
specimens hitherto figured by Petzholdt, Corda, Geeppert, Sternberg, 
Unger, and others, have generally wanted the cellular tissue of the 
axis and of the epidermis. The specimens which Mr. Binney has 
shown me exhibit, as I believe, the whole structure from the centre to 
the circumference. The axis (t. 55) consists of a considerable mass of 
cellular tissue without any vascular bundles penetrating it. This is 
surrounded by a solid cylinder of wood, formed entirely of scalariform 
vessels, and without (in all the specimens I have examined) any trace 
of medullary rays. The vascular tissue was developed from a series of 
equidistant points near the circumference of the cellular tissue, and 
grew outwards and laterally until they united in a continuous cylinder, 
fluted on the inner surface, and with the flutings filled with the cellular 
tissue of the axis. The early vascular bundles in the young stems of 
exogenous plants have a similar origin, but they speedily unite to form 
a woody cylinder, with a clearly defined and smooth inner surface 
towards the pith. This early condition is permanent in the stem of 
some arborescent species of Cactus, which, in this respect, closely re- 
sembles Calamites ; but it is only a similarity in the arrangement o 
the parts, without any true affinity, for the stems differ as much as 
idodendron does from Cycas. The woody cylinder formed constric- 
tions at regular intervals round the cellular axis, as in some recent 
Artocarpeæ. Beyond the woody cylinder there was a thin epidermal 
layer of parenchyma, which is less seldom preserved than even that of 
the interior. 
The flutings and constrictions of the stem described as external were 
on the interior of the woody cylinder. The parenchyma having gene- 
rally disappeared in fossilization, the wood alone formed the thin layer 
of coal that is generally all that remains to indicate the existence of 
the fossil. This is always furrowed longitudinally, and barred at 
intervals, apparently externally; but the examination of specimens, in 
which the structure is preserved, show that there was no fluting on 
the outer surface. Richter and Unger, in their * Paleontologie des 
