66 OUR NATIVE FERNS AND THEIR ALLIES. 



single small species of ground pine attests the existence of some 

 of the higher Cryptogamia ; no ferns, however, have been 

 found in America older than the Devonian. Over fifty species 

 of Devonian ferns have been described from the American 

 rocks chiefly, by Principal J. W. Dawson of Montreal. 



1 46. It is in the coal measures, however, that ferns and 

 other Cryptogamia are found in the greatest abundance and 

 profusion. Their delicate foliage is impressed on the various 

 rock strata above the beds of coal, and so perfectly are they 

 preserved that not only the methods of fructification but even 

 the microscopic spores have been detected ! In the coal meas- 

 ures of the United States and Canada (counting from the base 

 of the Catskill), 381 species of ferns have been described, 

 chiefly by Prof. Leo Lesquereux. The most abundant Ameri- 

 can genera are Neuropteris 45 species, Pecopteris 50 species, 

 Sphenopteris 31 species, Pseudopecopteris 25 species, and Rha- 

 cophyllum 24 species. 



The frontispiece gives an ideal representation of the vegeta- 

 tion of the Carboniferous age. The luxuriant tree-ferns, the 

 Lepidodendrids, ancient representatives of the diminutive club- 

 mosses or ground-pines, the Catamites, allies of the modern 

 scouring-rushes, and other forms no less wonderful, are seen in 

 their profusion. 



1 47. In the later geologic ages, Mesozoic and Tertiary, 

 ferns are found preserved in the rocks, with the leaves of many 

 trees and shrubs of existing genera. The indications are that 

 terns formed a far smaller part of the vegetation of these later 

 ages than in the preceding Carboniferous, and even approxi- 

 mated to that of the present. Six Cretaceous and twenty-four 

 Tertiary species have been catalogued,* including species in 

 the existing genera Lygodium, Pteris, Woodiuardia, Aspidium, 

 Gymnogramme, etc., as well as some related to genera abundant 

 in earlier formations. No living species is found fossil, unless 

 Dr. Newberry's variety of Onoclea sensibilis becomes estab- 

 lished .t In the course of geologic history, however, we can 



* Tenth report, Hayden Geological Survey of the Territories. Washing- 

 ton, 1878. 



t Prof. Lesquereux writes me: ''Though analogous by the nervation, I 

 doubt the identity on account of the coriaceous character of that fossil fern, 



