THE BOTANY OF A COAL MINE. 
297 
Is is singular however, to find that after being referred by some 
to Grymnosperms, and by others placed among the incertce 
sedis, the structure of the fruit shows that they really belong 
to the family to which at first, though on false observation, they 
had been referred. The stem, which as in Lepidodendron 
and Sigillaria in respect of their modern representatives, is 
anomalous when compared with the slender stems of recent 
equisetums, is yet only such a modification as would be re- 
quired for arborescent forms of the order. 
While the remains of Coniferce as distinct and recognisable 
fossils are rare in the coal measures, the abundance of coniferous 
structures in the “mother coal” shows that they formed a 
considerable proportion of the forests which flourished during 
the Carboniferous period. Large trunks have been found in 
sandstone beds, and fragments in which the structure is more 
perfectly preserved, are occasionally met with in nodules in the 
shale or in the coal itself. These exhibit in transverse section 
(fig. 10) a large pith, and the annual rings of growth character- 
istic of perennial exogenous plants ; and when cut parallel to 
the medullary rays, not only are the cells of the rays distinctly 
seen, but the disc-bearing tissue which is present in all known 
Coniferce . The discs occur in several parallel rows, unlike the 
common conifers of the northern hemisphere, in which they are 
always in a single series. They have on this account been 
referred to the araucarian type in the woody structure of which 
the same arrangement exists. In some specimens, referred to 
Dadoxylon , the supposed discs are rather reticulations (fig. 9) 
on the wall of the vessel, without the central pore which is a 
necessary part of the true disc-bearing tissue. Hooker has 
further elucidated the affinities of these fossil conifers by de- 
scribing a Trigonocarpon (fig. 11) which was preserved so as 
to exhibit structure. He gives satisfactory reasons deduced 
from its external appearance as well as its internal structure for 
considering it to be rather a coniferous fruit like the drupe of 
a Salisburia , than related to palms or cycads as had previously 
been supposed. He also points out the probability that the 
species of Noeggerathia described as the fronds of ferns, may 
have been the foliage of the same trees. So that here, as in 
Catamites and Lepidodendron , we seem to be able to construct 
from the scattered fragments this Salisburia-like conifer of the 
coal measures, finding its trunk in Dadoxylon or Pinites, its 
pith in Sternbergia , its foliage in Noeggerathia or Cyclopteris , 
and its fruit in Trigonocarpon ! 
The small number of genera, and even of species which have 
contributed to the formation of the beds of coal, is remarkable ; 
and it is probable that the progress of research will even yet 
greatly reduce both, but especially the number of species. The 
