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 Coniferae and in 

 the true fossil Coniferse, 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, Illicium 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 Goep- 

 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 

 II., fig. 10). These vessels (often with complete rounded or elliptical perforations, 

 owing to the disappearance of the walls) are seen evidently in Sigillarias ; and 

 Brongniart 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 II., figs. 8, 9), and not as in 

 coniferous wood (Plate II., 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 Sigil- 

 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 Lycopodiacese, and probably form a connecting link be- 

 tween them and Cycadacese. 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. 



I am also disposed to think that what Mr Quekett and Dr Bennett consider 



