32 THE DAWN OP LIFE. 



may be remains of plants, and in some specimens vermicular 

 lines, which I believe to be tubes of Eozoon penetrated by 

 matter once bituminous, but now in the state of graphite. 



" When palaeozoic 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 {Dadoxylon ouangondianum) 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 de- 

 tected in the Laurentian, though in the largest of the three 

 graphitic beds at St. John there appear to be fibrous struc- 

 tures which I believe may indicate the existence of land- 

 plants. This graphite is composed of contorted and slicken- 

 sided laminae, 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 ascertained 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 afiirmed that such tissues have 

 been found. It is possible, however, that in the Laurentian 

 period the vegetation of the land may have consisted wholly 



* Acadian Geology ^ p. 636. In calcified specimens the structures 

 remain in the graphite after decalcification by an acid. 



