OF THE FOSSIL PLANTS OF THE COAL-MEASURES. 
49 
have been about twenty-four in each verticil. This close correspondence between the 
leaves in my sections and the size, number, and arrangement of those of ordinary 
examples of Asteropliyllites is further maintained if we examine individual sections 
belonging to the former series. Plate III. fig. IT represents a group of such sections^ 
brought together from various specimens in my cabinet. It will at once be seen that these 
are generally identical with similar ones ( m , m') associated with Plate III. fig. 14. The 
diameters of these sections vary from -05 to -025, variations which would, of course, 
exist according to whether the sections were made obliquely near the broader part of 
the leaf or near its narrow and almost linear tip. In every instance the leaf consists 
of a single, very thick midrib, with two somewhat succulent and slightly incurved lateral 
margins. This is exactly the structure of the leaves preserved in ironstone nodules 
now in my cabinet, the Asterophyllitean character of which no one would venture to 
dispute. 
Amongst the numerous interesting specimens from Burntisland in Fifeshire for which 
I have been indebted to G. Grieve, Esq., was one which contained two stems, similar 
in many respects to those which I have just described. Careful search in other portions 
of the Burntisland rock revealed other specimens, showing that this plant had passed 
through stages of growth similar to those of our Lancashire type. But the distinctness 
of the two is demonstrated by the circumstance that, in the Oldham specimens, the 
vessels of the central axis are always reticulated , whilst those of the Burntisland species 
are as invariably barred. 
Plate III. fig. 18 is a transverse section of a young twig, obviously corresponding 
to Plate I. fig. 1. Its greatest diameter is about -017, and that of the largest of its 
vessels about *0029, dimensions which closely correspond with those of the Oldham 
plant. The bark (Jc) exists in this specimen, and I can readily make out its cellular 
structure ; but its outline is not so clearly defined as I could have wished, owing to the 
density of the vegetable mass in which it is imbedded. I see traces of the lateral 
grooves, especially at k, but these are not very definite. Some other specimens, how- 
ever, in the same stage of growth as fig. 18, exhibit these grooves very definitely, almost 
as much so as Plate I. fig. 1. Plate III. fig. 19 represents one of these, in which the 
triangle is somewhat more robust than in the previous example. The grooves {]<!) are 
here clearly shown on two sides of the specimen, the third having been accidentally 
broken off in making the section. The maximum diameter of this twig, including the 
bark, is -054, or rather more than Plate I. fig. 1. It will be noticed that, in this specimen, 
the angles of the central triangle are distinctly truncate, reminding us of the same con- 
dition in VolJcmannia Dawsoni. The next stage of growth in which I find this plant is 
represented in Plate III. fig. 20. The central triangle has now enlarged to *054, and the 
diameter of its largest vessels to -005. The exogenous layers are three or four in number. 
In their general arrangement these layers correspond with those of the Lancashire type, 
but with the apparently specific distinction that the vessels of the former are much 
more uniform in size and less regular in their arrangement than those of the latter. 
MDCCCLXXIV. 
H 
