OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
505 
The central portion of the vascular axis, a, is composed, as previously described, of the 
ordinary group of barred vessels. The exogenously developed layer is produced into 
three prominent lobes, b, b, b. The component radiating laminm of each lobe are 
more or less curved, their concavities being directed towards the centre of each lobe. 
The result of this arrangement is to exhibit in a new manner the tendency towards a 
triquetrous arrangement which I have already shown to be a characteristic feature of 
some of these strobili whenever we obtain them in anything approaching to a perfect 
condition. 
In the sporangia of this specimen, which is from the Halifax bed, we find beautiful 
examples of numerous mother-cells, each of which exhibits three, but doubtless contains 
four daughter-cells. These latter appear to me to be the true spores since they cor¬ 
respond, so far as size is concerned, with most of those seen in my numerous other 
sections of this fruit. A second specimen from Halifax, for which I am indebted to 
Mr. Binns, exhibits this condition of the spores yet more perfectly. Fig. 17 represents 
one of the mother-cells of this example, enlarged 400 diameters. Its three contained 
daughter-cells are perfect in their outlines; those in Mr. Spencer’s section are more 
shrivelled and ruptured. In none have we a trace of elaters. In the slide containing 
Mr. Binns’ specimen is an obliquely transverse section of another strobilus of which 
the axis has had the same structure as that represented in fig. 16, It displays four of 
its sporangia, all of which are filled with parenchyma, in which no spores or daughter- 
cells are yet visible. The sporangium walls, fig. 18, a, are strongly defined, and the 
parenchyma, b, entirely fills the cavity of each sporangium, differing in this respect 
from most of the other examples which I have seen. This absence of daughter-cells 
from each of the parenchymatous cells obviously suggests that we here have the 
strobilus in a very young state ; yet we find that, in its axis, the peripheral radiating 
vascular laminae seen in fig. 16, b, are already present. This fact seems to show that 
we have at least two species of these fruits, distinguished from each other by these 
differences in the structure of the central axis, but identical in every other respect; 
both being equally characterised by a tendency on the part of the vascular axis to 
assume more or less distinctly the triquetrous form. 
Ferns . 
The Halifax beds have furnished two new forms of fern-stems or petioles. Of the 
first of these, of which a transverse section is represented in fig. 23a, I have received 
sections both from Mr. Spencer, of Halifax, and from Mr. Earnshaw, of Oldham. In 
its essential features this agrees with many of the other Rachiopterid.es which I have 
already described. Its chief characteristic resides in the form of its very large oval 
vascular bundle winch consists of a dense mass of thick-walled barred vessels. Its 
maximum diameter is about Tl. I propose to distinguish it by the provisional name 
of Raehiopteris robusta. 
