FOUND IN COAL FROM FORDEL. 189 
he restricts his term coal to a substance formed of woody tissue of this nature. 
As regards this point, I think he has come to a conclusion which is not con- 
firmed either by the external configuration or by the internal structure of the 
plants concerned in the formation of coal. The true characters of the coniferous 
wood are the circular markings, with the dot in the centre, and hence the name 
punctated or disc-bearing. This structure is seen both in recent Coniferze and in 
the true fossil Conifereze, such as the Dadoxylons of the sandstones in this 
neighbourhood. It is not however restricted to Conifers, for it has been detected 
in Drimys Winteri, Ilicium floridanum, and other plants. This punctated struc- 
ture is not easily demonstrated in the coal of the carboniferous epoch, although 
it has been detected in the brown coal of the tertiary beds, according to Gorp- 
PERT, and in the needle-coal of Bohemia (Plate II., fig. 5). What has been con- 
sidered as punctated tissue in coal appears to be, in many instances, dotted or pitted 
vessels (Plate II., figs. 6-9), some of which assume a scalariform appearance (Plate 
IL., fig. 10). These vessels (often with complete rounded or elliptical perforations, 
owing to the disappearance of the walls) are seen evidently in Sigillarias; and 
Bronenrart has figured them in his account of Sigillaria elegans. They occur in 
Arniston, Newbattle, and other coals, found in the neighbourhood of Edinburgh ; 
and now that I have seen them in the Fordel coal, in the very substance of Sigil- 
laria, I look upon them as the pitted vascular tissue of that plant. In Fordel 
and other coals, we also meet with true scalariform vessels (Plate II., fig. 11), 
which may be looked upon as intermediate between spiral and pitted tissue. 
~ In some specimens of Fordel coal, where the impressions of Sigillaria are very 
evident, there is no difficulty in seeing under the microscope these pitted vessels, 
having their walls covered with perforations (Plate IL., figs. 8, 9), and not as in 
coniferous wood (Plate IL., fig. 5), where the punctated discs are confined to two 
sides of the tubes, and can only be seen properly when the section is made in the 
line of the medullary rays. The absence of central punctation, the general distri- 
bution of the perforations over the walls, and their close approximation, all, in my 
opinion, show the tissue to be pitted vessels (Bothrenchyma or Taphrenchyma), 
and not punctated woody tubes. 
We have, then, in my opinion, evidence here, both from external characters 
and microscopic texture, that the plants forming Fordel coal were in part SicIL- 
LARIAS. The question then comes, What are these Sigillarias? Fossil botanists 
place them among Acrogens, and in the immediate vicinity of Ferns. They seem 
to have a close affinity to Lycopodiaceze, and probably form a connecting link be- 
tween them and Cycadaceze. We have the scalariform tissue of the one, and the 
dotted tissue of the other. This appears to me to be a very interesting result of 
microscopic investigation; and I think we shall be confirmed in this opinion by 
what I have further to state in regard to Fordel coal. 
1 am also disposed to think that what Mr Quexert and Dr Bennett consider 
