[O2 THE HISTORY OF CREATION. 
In their organization Ferns rise considerably above Mosses, 
and in their more highly developed forms even approach the 
flowering plants. In Mosses, as in Thallus plants, the entire 
body is composed of almost equi-formal cells, little if at all 
differentiated ; but in the tissues of Ferns we find those 
peculiarly differentiated strings of cel’; which are called the 
vessels of plants, and which are universally met with in 
flowering plants. Hence Ferns are sometimes united as 
“vascular Cryptogams” with Phanerogams, and the group 
so formed is contrasted as that of the “vascular plants” 
with “cellular plants,’—that is, with “ cellular eryptogams” 
(Mosses and Thallus plants). This very important process 
in the organization of plants—the formation of vessels 
—first occurred, therefore, in the Devonian period, con- 
sequently in the beginning of the second and smaller half 
of the organic history of the earth. 
The branch of Ferns, or Filicinz, is divided into five 
distinct classes: (1) Frondose Ferns, or Pteride; (2) Reed 
Ferns, or Calamaria; (3) Aquatic Ferns, or Rhizocarpez ; 
(4) Snakes Tongues, or Ophioglosse; and (5) Scale Ferns, 
-or Lepidophyta. By far the most important of these five 
classes, and also the richest in forms, were first the Frondose 
Ferns, and then the Scale-ferns, which formed the princi- 
pal portion of the palzeolithic forests. The Reed Ferns, on 
the other hand, had at that time already somewhat 
diminished in number ; and of the Aquatic Ferns, we do not 
even know with certainty whether they then existed. It is 
difficult for us to form any idea of the very peculiar 
character of those gloomy palzolithic fern forests, in which 
the whole of the gay abundance of flowers of our present 
flora was entirely wanting, and which were not enlivened 
