FOSSIL FLOKA OF THE CAEBONIFEEOUS SYSTEM. 729 



and a Calamite have been discovered by him. In the Old Eed Sand- 

 stone rocks at Oporto, Bunbury detected Pecopteris Cyathea, P. 

 muricata, and Neuropteris tenuifolia — ferns allied to those of the 

 Coal-measures. A still more extensive and varied land flora of 

 Devonian age (or Erian, as he calls it) has been described and illus- 

 trated by Principal Dawson from the rocks of that period occurring 

 in Canada ; and during a recent visit to Britain he has correlated 

 many of the fragments collected by Miller, Peach, and 'others,- with 

 the American species he has described. The following are some of 

 the fossil plants from beds older than the Carboniferous system : — 

 Prototaxites Logani, Dadoxylon ouangondianum, Calamites transi- 

 tionis, Asterophyllites parvulus, Sphenophyllum antiquum, Lepido- 

 dendron Gaspianum, Lepidostrobus Eichardsoni, L. Matthewi, Psilo- 

 phyton princeps, P. robustum, Selaginites formosus, Cordaites Robbii, 

 C. angustifolius, Oyclopteris Jacksoni. 



Fossil Floea of the Caebonipeeous System. — The Carboni- 

 ferous period is one of the most important as regards fossil plants. 

 The vegetable forms are numerous and uniform throughout the whole 

 system, whether exhibited in the Old or the New World. The im- 

 portant substance called Coal owes its origin to the plants of this 

 epoch. It has been subjected to great pressure, and hence the 

 appearance of the plants has been much altered. It is difficult to 

 give a definition of Coal. The varieties of it are numerous. There 

 is a gradual transition from Anthracite to Household and Parrot 

 Coal, and the limit between Coal and what is called bituminous shale 

 is by no means distinct. Coal may be said to be chemically-altered 

 vegetable matter interstratified with the rocks, and capable of being 

 used as ftiel. On examining thin sections of coal under the micro- 

 scope, we can detect vegetable tissues both of a cellular and vascular 

 nature. In Wigan cannel coal vegetable structure. is seen throughout 

 the whole mass. Such is likewise the case with other cannel, parrot, 

 and gas coals. In common household coal, also, evident traces of 

 organic tissue have been observed. In some kinds of coal punctated 

 woody fibre has been detected, in others scalariform tissue, as well as 

 cells of different kinds. Sporangia are also occasionally found in the 

 substance of coal, as shown by Mr. Daw in that from Fordel; and 

 some beds, like the Better bed of Bradford, are composed almost 

 entirely of these sporangia, embedded in their shed microspores, as 

 has been recently shown by Huxley. The structure of coal in different 

 beds, and in different parts of the same bed, seems to vary according 

 to the nature of the plants by which it has been formed, as well as 

 to metamorphism. Hence the different varieties of coal which are 

 worked. The occurrence of punctated tissue indicates the presence of 

 Coniferse in the coal bed, while scalariform vessels point to Ferns and 

 their allied forms, such as Sigillaria and Lepidodendron. The ana- 



