SALTER A CHRISTMAS LECTURE ON COAL. 



129 



Fir trees of one sort or another were abundant in the coal-period, 

 and have been so in every succeeding formation. But here, as in 

 every other case, the coal-trees were different from the modern ones. 

 Now we have abundant spruce, and larch, and fir ; junipers, and 

 cypress trees, and yews ; and in the tertiary and oolitic times these 

 were common trees. But the Araucaria tribe, to wliich the graceful 

 Norfolk Island pine belongs, is only to be. met with rarely. At least 

 it is confined to a small portion of the globe- In the coal time it 

 was the prevailing form. There is no need to give a drawing of the 

 structure of this wood, for it has been given by every author who has 

 written on the coal. 



Wood is made up long fibres, which fibres communicate with each 

 other by pores. The wood of coniferous trees is specially remarkable 

 for the large disks which surround these pores. They are disposed in 

 straight rows, and most of the Goniferce have only a single row. But 

 the Araucarioe have a double row — or more than a double row ; and 

 all the coal fir-trees are of this kind. 



Again there is a remarkable difference between the coal-trees and 

 their living representatives. In no living fir-tree does the pith show 

 of any size, except in quite the young shoots. After that age it 

 gradually diminishes in diameter, or rather does not increase with the 

 growth of the tree, being pressed upon by the successive layers of the 



Coniferous wood f DadoxylonJ, with its pith, Sterubergia leaves f Cyclopteris,/, pro- 

 bably of the same coniferous tree ; fruit and seeds f Trigonocarpum) of the same. 



wood, till in a cross cut of a piece of fir a mere trace of this substance? 

 so important in the first stages of the young branch, is to be seen. 

 The case is different with the old fir-trees of the coal. Here (accord- 

 ing to the excellent observations of Dr. Williamson, of Manchester), 

 the pith is of enormous size, and retains that size during the after- 

 stages of growth, if it does not actually increase. It was long ago 

 known under the name of Sternbergia, and is often as thick as a large 

 man's thumb, or even thicker. I have seen some as thick as a child s 

 wrist. 



VOL. iv. R 



