Haunts, Habits, and Distribution. 25 



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 roclcs chiefly, by Dr. J. W. 

 Dawson of Montreal. 



It is in the coal measures, however, that ferns and other Cryp- 

 togamia 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 measures of the United States and 

 Canada (counting from the base of the Catskill), three hundred 

 and eighty-one species of ferns have been described, chiefly by 

 Prof. Leo Lesquereux. The most abundant American genera are 

 Neuropteris 45 species, Pecopteris 50 species, Sphenopteris 31 spe- 

 cies, Pseudopecopteris 25 species, and Rhacophyllum 24 species. 



The frontispiece gives an ideal representation of the vegeta- 

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

 idodendrids , ancient representatives of the diminutive club mosses 

 or ground pines, the Catamites, allies of the modem scouring- 

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

 fusion. 



In the later geological 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 ferns formed 

 a far smaller part of the vegetation of these later ages than in the ■ 

 preceding Carboniferous, and even approximated to that of the 

 present. Six Cretaceous and twenty-four Tertiary species have 

 been catalogued,* including species in the existing genera Lygo- 

 dium, Pteris, Woodwardia, 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 established.! In the course of geo- 

 logical history, however, we can trace a gradual approximation to 

 the modern types from the generalized forms of Devonian and 

 Carboniferous times. 



* Tenth Report, Haydea Geological Survey of the Territories, Washington, 1878. 



t Prof. Leaquereux writes me : " Though analogous by the nervation, I doubt the 

 identity on account of the coriaceous character of that fossil fern, which I have not seen 

 in any variety of 0. sensibilis now living." 



