PART I. 
EXPLANATION OF THE NATURE AND STRUCTURE OF THE PARTS 
OF FERNS ON WHICH GENERA ARE FOUNDED AND CLASSIFIED. 
1.—NATURE AND NUMBER OF FERNS. 
Tae plants which form the subject of this volume con- 
stitute a special Order in the Vegetable Kingdom, termed 
Filices, popularly known by the name of Ferns; they are 
plants of special habit and structure, and rank ont: in 
the class Cryptogamia of Linnseus. : 
= - From circumstances explained hereafter, the number of 
species representing the present Fern flora is not well 
ascertained ; it is sufficient here to say that about 2,500 
. have been described in books by different botanists, speci- 
mens of nearly that number being preserved in the princi- 
. pal herbaria of Europe, of which about a thousand have 
been introduced in a living state, and cultivated in the 
ihe gardens of this country. "They are widely spread over ` = 
_ the earth, being found in the tropics and temperate regions, - 
. and extending nearly to the limits of vegetable life in both - 
the northern and southern hemispheres. In habit and — E 
mode of growth the greater number come under the 
category of herbaceous perennials, having seasons of ` ` = 
- growth and rest according with the nature of the dif 
