KEY TO THE GENERA. 



307 



SECTION II. 



(Sporangia on the under side of the fronds.) 



** INDUSIUM WANTING. 



PACK. 



Polypodium 



3. Fruit-dots roundish, large ; evergreen, 

 rock species. Polypody. 



POLYPODIUM. 196 



3, Fruit-dots roundish, small ; fronds 

 triangular. Beech ferns. 



PHEGOPTERIS. 200 



3. Fruit in lines on the margins of the 

 pinnules ; under surface of the 

 fronds covered with 'whitish pow- 

 der. NOTHOL^ENA. 288 



INDUSIUM PRESENT. 

 ** 



Sori on the edge of the pinnule ; spor- 

 angia sessile at the base of a long 

 bristle-like receptacle and sur- 

 rounded by a funnel form, slightly 

 two-lipped involucre. Filmy fern. 

 TRICHOMANES. 



289 



TVichomane* 



