THE PRIMITIVE VEGETATION OF THE EARTH. 477 
cases. The root-stocks must in many cases have matted the 
soils in which they grew into a dense mass of vegetable 
matter, and in some places they accumulated to a sufficient 
extent to form layers of coaly matter, one of which on the 
south side of Gaspé Bay is as much as three inches in thick- 
ness, and is the oldest coal known in America. More 
usually the root-beds consist of hardened clay or fine sand- 
stone filled with complicated net-work or with parallel bands 
of rhizomes more or less flattened and in various states of 
preservation. In all probability these beds were originally 
swampy soils. From the surface of such a root-bed there 
arose into the air countless numbers of slender but somewhat 
woody stems, forming a dense mass of vegetation three or 
four feet in height. The stems, when young or barren, were 
more or less sparsely clothed with thick, short, pointed 
leaves, which, from the manner in which they penetrate the 
stone, must have been very rigid. At their extremities the. 
stems were divided into slender branches, and these when: 
young were curled in a crosier-like or circinate manner. 
When mature they bore at the ends of small branchlets pairs 
of oval sacs or spore-cases. The rhizomes when well pre- 
served show minute markings, apparently indieating hairs or 
scales, and also round areoles with central spots, like those 
of Stigmaria, but not regularly arranged. These curious 
plants are unlike anything in the actual world. I have com- 
pared their fructification with that of the Pilularie or Pill- 
worts, a comparison which has also occurred to Dr. Hooker. 
On the other hand, this fructification is borne in a totally 
different manner from that of Pilularia, and in this respect 
rather resembles some ferns; and the young stems by them- 
selves would be referred without hesitation to Lycopodiacez. 
In short, Psilophyton is a generalized plant, presenting char- 
acters not combined in the modern world, and, perhaps 
illustrating what seems to be a general law of creation, that 
in the earlier periods low forms assumed characteristics 
subsequently confined to higher grades of being. 
