from Macquarie Plains. 
25 
merely remark, that it is imbedded in a trappean rock : 
its position and appearance are too well known to require 
any description from so casual a visitor as I was. 
The bark (?) is of a different colour and more consoli¬ 
dated than the interior, resembling the most beautiful 
agate. The woody part reminded me of the lignite, so 
common in Lough Neagh, in the north of Ireland, and 
which consists of the silicified remains of a part of the 
ancient forest of Scotch fir that once extended over that 
part of Ireland. The most remarkable circumstance, how¬ 
ever, connected with this fossilized tree, is the manner in 
which the outer layers of wood, when exposed by the re¬ 
moval of the bark, separate into the ultimate fibres of 
which it is composed, forming an amianthus-like mass on 
the ventricle of the stump in one place, and covering the 
ground with a white powder, commonly called here 
native pounce. The examination of a single concentric 
layer from this part shows that it may be detached from 
the contiguous layers of the preceding and following 
year s growth ; there being no silicious matter infiltrated 
into the intervening spaces. A portion of each layer is 
found to have a second cleavage, not concentric with it, 
but in the direction of its radius, or of a line drawn from 
the centre to the bark of the tree. Such a cleavage is 
to be expected from the fact, that it is in the direction of 
the medullary rays that traverse every where the woody 
tissue. Each of these laminae is of extreme tenuity, of 
indeterminate length, and of the breadth of the layers of 
wood; and is formed of a single series of parallel woody 
fibres, crossed here and there by the cellular tissue of the 
medullary rays, which do not generally interfere with 
their regularity. These plates, again, are separable into 
single minute fibres, which are elongated tubes of pleu- 
renchyma or woody tissue, tapering at either end into 
conical terminations of indefinite length. They lie 
