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. 



THE 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 highest in 

 the class Cryptogamia of Linnaeus. 



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 

 the 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 

 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- 

 ferent climates they inhabit, 

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