116 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 
what may be regarded as natural injections, sometimes of much 
beauty. In correspondence with this, while in some Laurentian 
graphitic rocks, as, for instance, in the compact graphite of Cla- 
rendon, the carbon presents a curdled appearance due to segregation, 
and precisely similar to that of the bitumen in more modern bitu- 
minous rocks, I can detect in the graphitic limestones occasional 
fibrous structures which may be remains of plants, and in some 
specimens vermicular lines, which I believe to be tubes of Hozoon 
penetrated by matter once bituminous, but now in the state of 
graphite. 
When paleozoic land-plants have been converted into graphite, 
they sometimes perfectly retain their structure. Mineral charcoal, 
with structure, exists in the graphitic coal of Rhode Island. The 
fronds of ferns, with their minutest veins perfect, are preserved in 
the Devonian shales of St. John, in the state of graphite; and in the 
same formation there are trunks of Conifers (Dadoaylon onangon- 
dianum) in which the material of the cell-walls has been converted 
into graphite, while their cavities have been filled with calcareous 
spar and quartz, the finest structures being preserved quite as well 
as in comparatively unaltered specimens from the coal-formation*. 
No structures so perfect have as yet been detected in the Laurentian, 
though in the largest of the three graphitic beds at St. John there 
appear to be fibrous structures, which I believe may indicate the 
existence of land-plants. This graphite is composed of contorted 
and slickensided lamine, much like those of some bituminous 
shales and coarse coals; and in these there are occasional small 
pyritous masses which show hollow carbonaceous fibres, in some 
cases presenting obscure indications of lateral pores. I regard these 
indications, however, as uncertain ; and it is not as yet fully ascer- 
tained that these beds at St. John are on the same geological horizon 
with the Lower Laurentian of Canada, though they certainly underlie 
the Primordial series of the Acadian group, and are separated from 
it by beds having the character of the Huronian. 
There is thus no absolute impossibility that distinct organic tissues 
may be found in the Laurentian graphite, if formed from land-plants, 
more especially if any plants existed at that time having true woody 
or vascular tissues; but it cannot with certainty be affirmed that 
such tissues have been found. It is possible, however, that in the 
Laurentian period the vegetation of the land may have consisted 
wholly of cellular plants, as, for example, mosses and lichens; and 
if so, there would be comparatively little hope of the distinct pre- 
servation of their forms or tissues, or of our being able to distinguish 
the remains of land-plants from those of Alge. 
We may sum up these facts and considerations in the following 
statements :—First, that somewhat obscure traces of organic struc- 
ture can be detected in the Laurentian graphite; secondly, that the 
general arrangement and microscopic structure of the substance cor- 
responds with that of the carbonaceous and bituminous matters in 
* Acadian Geology, p. 535. In calcified specimens the structures remain in 
the graphite after decalcification by an acid. 
