HISTORY OF THE VEGETABLE KINGDOM, 621 
the age, were of highly specialized types. I do not say that these were not 
evolved from the low, protozoan types, that probably existed during eozoic times. 
I do not know how they were introduced. It may have been by evolution, but of 
this we have no evidence worthy of being called scientific. But, according to a 
principle already stated, we know the existence of such an extensive fauna de- 
manded an enormous development of the vegetable kingdom to furnish, either 
directly or indirectly, sustenance for the numerous animals that thronged the Si- 
lurian seas. Unlike the previous age, we have in the rocks of the Silurian age 
numerous fossil vegetables, not only furnishing positive proof that they existed 
in that age, but also giving us an idea of their forms and structure. The plants of 
this age were, with very few exceptions, marine algee. -There are a few examples 
of land plants, the remains of which have been found in rocks belonging to this 
age. Recently two fossils from the lower Silurian in Ohio have been described as 
land plants of the genus Sigillaria ; but the correctness of this conclusion has been 
called in question by very high authority, so that they are not to be permitted, for 
the present, to testify to the existence of such highly specialized plants at that early 
day. The only objection to giving these fossils their high position is their lack of 
decided characteristics to justify their claims to such honor. The remains of what 
are claimed to be land plants have been found in the rocks of this age in Sweden. 
All geologists claim that they are not algz, and they are referred to as vascular 
cryptogams and monocotyledons. If this be their true character, we have here, 
even inthe lower Cambrian, quite highly developed land plants. The trouble 
with all these specimens is, they are so void of distinguishing characteristics that we 
are liable to mistake a Thallogen for some ofthe more highly differentiated orders 
of plants. In Scotland there are traces of the remains of land plants in the lower 
Silurian ; but their characteristics are not very positive, and, at best, they must 
have belonged to some humble class of endogenous plants. Undoubted land 
plants have been found in Canada, where, with a large number of fucoids, 
a few specimens of club-mosses have been discovered, that are referred to Prof. 
Dawson’s genus Psdlophyton. 
In these both the fibrous bark and the scatariform axis remain and serve to 
guide to a proper classification. Such are all the evidences known of the exist- 
ence of land plants during the Silurian age, and it must be confessed they are 
exceedingly meager, though in view of the fact that there was a large V shaped 
tract of land above the ocean between what are now the St. Lawrence river and 
Hudson’s Bay, it is extremely probable that during the long time that intervened 
between the elevation of this land and the close of the Silurian age many land 
plants flourished, considerable numbers of which would be floated off and buried 
in thesediment of the Silurian seas. Much ofthis doubtless remains to be discovered. 
“Next above the Silurian comes the Devonian Age in which, in addition to the 
humble plants noticed above, we find those of higher organization and more 
complex structure. These include all the orders of vascular cryptogams, viz: 
ferns, lycopods and equisetae. The Ferns were represented by a number of gen- 
