OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
small botryoidal granules (some infiltrated) of ferruginous oxide, which have loosely 
and imperfectly filled the cavities separating the medullary disks. This explanation is 
the more probable since the entire specimen was originally enclosed in a nodule of the 
ordinary Clay Ironstone so common in the Coal-measures of Coalbrookdale. There is no 
doubt whatever that these cellular laminae are identical with those of the ordinary 
forms of Sternbergia, only more closely aggregated than is usual with specimens of 
larger size. 
The ligneous part of the stem is a cylinder of wood-fibres (figs. 33 & 35, 5), the thick- 
ness of the cylinder from the medulla to the bark being about '05. At its innermost 
surface, b', we find a few very small, but distinct, barred vessels occupying the position of 
a medullary sheath, which element of exogenous stems they apparently represent : three 
of these vessels are enlarged in fig. 37. In the transverse sections the vessels are 
arranged in very regular radiating lines. They have a mean diameter of ‘0012, which 
corresponds with those of Salisburia adiantifolia and Araucaria JBraziliensis ; but their 
walls are thinner than in the corresponding twigs of either of those living Conifers. 
These vessels terminate in fusiform extremities. Their length varies, but many of them 
are not more than ’012 ; others are somewhat longer. These proportions show that the 
tubes do not differ materially from the ordinary woody prosenchyma of living Conifers. 
The magnified representations (figs. 38 & 39) show that the two surfaces which are 
parallel with the medullary rays are marked with very regular geometric areolse, each of 
which has a mean vertical diameter of ‘0005. Their transverse diameter varies. Some- 
times a single row runs down the centre of each fibre, each areole then stretching across 
almost the entire diameter of that fibre. In others, as in fig. 39, which represents their 
ordinary arrangement, we have two such rows. Occasionally, as seen in fig. 38, there 
are three vertical series of these areolse. On turning to the tangential sections, fig. 40, 
we obtain in the beaded lines, g, g, clear proof that these areolse are not those of ordinary 
reticulated fibro-vascular tissue, but true bordered pits, to the formation of which, as 
explained by Sachs, reference has already been made*. In the plant under consideration 
there is no central aperture in each of these areolar pits, such as is usually seen in living 
Coniferous plants ; Sachs's explanation of their origin supposes that secondary deposits 
are formed within each fibre, but that there are thin circular spaces within each fibre 
in which the deposit does not rest upon the primitive cell-wall, but gradually rises up 
from it, like a circular dome, in the centre of which there remains a small, unclosed 
aperture, like that left for the reception of a skylight in a dome-shaped roof. 
Sachs further shows that similar deposits take place at exactly corresponding points 
on the cell-walls of two contiguous fibres. Such growths would form two opposed semi- 
lenticular or plano-concave cavities, with the two thin coalesced cell-walls separating 
them. These latter become absorbed in living plants, so that the two plano-concave 
spaces become converted into one double concave one. In figs. 38 & 39 we see that no 
central aperture exists in each areole. Here nature has set the example to a builder 
* Lehrbuch der Botanik, pp. 26, 27. 
