22 Our Native Ferns. 



tropical continental areas with insular climates. The little island 

 of Mauritius having an area of 676 square miles, or less than one-, 

 third the area of Delaware, has 235 native species, while Java, 

 little larger than New York; has 460. Brazil furnishes 387, and the 

 Isthmus of Panama 117; Comparing these with colder climates, 

 we find 67 in all Europe, and oVily 26. within the borders of the 

 arctic zone. - • 



" Our Native Ferns," as described later in this' volume, includ- 

 ing the botanical orders, Filices and Ophioglossace^, com- 

 prise 147 species, 15 varieties, and 6 sub-varieties. Some authors 

 recognize more varieties, .and others even recognize more species. 



ig. Divisions of our Fern Flora. — It has been found con- 

 venient to divide the surface of the earth into faunas and floras, 

 limited by the natural distriBution of the various species of ani- 

 mals and plants. These liniits are by no means sharply defined, for 

 wherever the limit is made some species will pass beyond it ; yet 

 the majority found one side are different from the majority of those 

 on the other. North America (excluding Mexico), forms the 

 Nearctic realm or fauna {Regnum Nearciicum), and the same 

 boundaries may be used in the limitation of our fern flora, although 

 some species from tropical regions invade our southern borders. 



Mr. J. H. Redfield has given us a distribution of our native 

 species into six geographical divisions or subdivisions of the Ne- 

 arctic realm, from which the following section is copied.* 



20. " I. Cosmopolitan : widely distributed over the globe in 

 both temperate and tropical regions. 



II. Boreal : inhabiting (with a few exceptions) the nofth- 

 ern portion of the United States, extending through Canada and 

 British America, some species even reaching Labrador, Greenland 

 and Alaska, and nearly all represented also in the northern por- 

 tions of the Old World. 



III. Appalachian: extending throughout the mountain 

 and hilly region of the states east of the Mississippi, often to the 

 coast, and northward into Canada, and in a few instances also in- 

 habiting the Old World. 



IV. Pacific: extending along the western border of the 

 continent at points from Alaska to California, in a few cases ap- 

 pearing also in the Rocky Mountain region. 



* Bulletin Torroy Botanical Club, January, 1815. 



