THE PALEONTOLOGIC RECORD 337 
lution, it is as yet by no means adequate with respect to meeting all that 
theory demands. For this there is an intelligible explanation based in 
part upon the fact that the necessary material is available only under 
conditions of great difficulty; and that the character of the remains 
upon which research is based is conditioned by the original nature of 
the structure and its ability to survive in an unaltered form, the re- 
markable conditions of decay, infiltration, compression, upheaval and 
often of volcanic influences to which it has been subjected. The earliest 
type of vegetation was that which we now find in hot springs, continued 
with the alge found in cool or cold waters, all of which possessed a deli- 
cacy of structure which permitted speedy decay. The great abundance 
of such organisms probably afford an adequate explanation of the 
Laurentian and later forms of graphite which is regarded by many as 
the remains of former vegetation. While this hypothesis may be ac- 
cepted provisionally, paleobotany is nevertheless wholly unable to fur- 
nish any clue to the life history of the individuals, or even to inform 
us as to the specific types. Such knowledge as we possess in this direc- 
tion is the result of inference from parallel conditions and structures 
as now found. 
It might be assumed that with an increasing perfection in the pres- 
ervation of fossil remains, as found especially in the later formations, 
it should be possible to trace the course of descent with accuracy and 
completeness. This is, in a measure, true, but although the general re- 
quirements of theory may be verified, yet the haphazard conditions 
involved in the collection of plant remains make it a very difficult mat- 
ter to secure a complete narrative, and there remain many gaps which 
it is difficult to fill. The evolutional position of the Bryophytes de- 
mands that the origin of these plants should lie somewhere in the early 
Silurian or even in the Eozoic age, but we have no certain knowledge 
of them until the middle Mesozoic, and their remains do not become 
familiar or abundant until the later Tertiary. So important a devia- 
tion from what theory demands should lead us to caution in drawing 
conclusions from the direct testimony which is thus presented. Unless 
otherwise disposed of through paleontological evidence, it would be 
more correct to infer that the delicacy of the plants, and the conditions 
of their fossilization, have not admitted of their preservation in a recog- 
nizable condition ; while there is also the further probability that many 
of their remains have been overlooked through resemblance to certain 
Pteridophyta for which they might well be mistaken. 
In spite of such apparent contradictions, the evidence everywhere 
points with great force to the idea that each of the lesser phyla had its 
origin in some ancestral form, followed by growth and culmination. 
This latter was, in some cases, abrupt, as in many of the Pteridophytes ; 
in other instances there was a gradual decline, as in the lycopods or the 
horsetails, which attained their highest development in the later Paleo- 
