9 INTRODUCTION. 
by their external forms; and in many instances, these forms are obviously 
too much altered, to permit us to refer the objects in question, with perfect 
satisfaction, to any natural family. But a method has lately been disco- 
vered, by which the stems or branches may be sliced, and afterwards reduced 
to such a degree of thinness as to permit us to inspect the most minute re- 
mains of organic texture. The unexpected result thus obtained, has en- 
abled me to examine numerous varieties of structure in fossil plants; and I 
feel confident, that I should be rendering a service to science, by presenting 
to the public representations of some of these varieties, accompanied by others 
of those recent plants to which they seem decidedly to approximate. 
According to the opinion of those who have most successfully cultivated 
geological botany, the essential character of the first vegetation of the globe 
consisted in the great development and numerical preponderance of the vas- 
cular cryptogamic plants; and the great size of the Ferns, Lycopodiacez, 
and Equisetacez, imbedded in our deposits, authorize us to presume, that, 
during that period, circumstances calculated to favour the development of 
these plants had prevailed in a very high degree, May we not now goa 
little farther, and, from the recent discoveries, suppose that heat and moisture 
had an equal effect upon plants of different genera from those of the vas- 
cular cryptogamic ? When we discover stems of fossil plants thirty, 
sixty, and even seventy feet long—when each torrent by its violence un- 
covers so many relics of ancient times—nay, whenever, by the busy inge- 
nuity of man, the lower as well as the higher sedimentary deposits are in- 
terfered with or disturbed, some previously unobserved fossil is discovered, 
it is but fair to conclude that the same causes have equally affected them. 
By the investigations of many of my friends, and by my own observa- 
tions, I am induced (as already noticed) to think that plants of the phane- 
rogamic class will be found to occur in greater abundance in the earlier se- 
dimentary deposits than was before believed. The day is now arrived, when 
doubts and difficulties as to the class and family to which they are to be re- 
ferred, must give way under the microscopic examination of the internal 
structure of these fossil plants; and I am happy in having it in my power 
to contribute in some degree to the elucidation of this interesting subject. 
