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, 
^^ow 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 Araiicaria tribe, to which 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 Gontferce have only a single row. But 
the Araucarice 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 ^Dadoxylon;, with its pith, Steruberpfia leaves ^Cyclopteris^, pro- 
bably of the same coniferous tree ; fruit and seeds ^Trigonocarpum) of the same. 
wood, till in a cross cut of a piece of fir a mere trace of this substance 5 
so important in the first stages of the young branch, is to be seen. 
The case is difierent 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 actaally increase. It was long ago 
known under the name of Sternhergia, 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. K 
