198 



THE POLYPODIES. 



cristatum with pinnules variously forked and crested. 

 A form from West Virginia has recently been described 

 as /*. vulgare deceptum. It differs from the common 

 form in being somewhat larger with narrower, pointed 

 pinnae. This was earlier considered a mere form and 

 named bis erratum. Considering the unimportant differ- 

 ences it displays, the earlier view seems the correct one. 

 In North America the polypody is 

 found from Alabama to the far north 

 and northwestward. Its natural habi- 

 tat is upon rocks but it is occasionally 

 found upon trees and logs where the 

 atmosphere is moist. In the moister 

 climate of England, it is said to be very 

 commonly found on trees. In our 

 western States, it is rare or absent, 

 but its place is taken by several allied 

 species that much resemble it. It is a 

 tough and hardy species able to en- 

 dure great extremes of temperature 

 and is found in nearly all parts of the 

 world. 



The Gray Polypody. 



The little gray polypody (Poly po- 

 dium incanuni] may be termed a strag- 

 gler into our territory from a warmer 

 region. It is most abundant in the 

 Tropics, where it grows on rocks, trees, 

 walls and even on the roofs of the 

 houses. In the northern part of its 

 range, it is usually found on rocks or about the roots of 



GRAY POLYPODY. 

 Polypodium incanum 



