Filices Polypodium. 551 



which is derived from TroXuy, many, and TroOy, a foot, probably in 

 allusion to the numerous creeping rhizomes of P. vulgare. 



1. P. vulgare. This Fern is readily distinguished from all 

 other native species by its creeping densely scaly aboveground 

 rhizomes and alternate pinnatifid glabrous stipitate fronds with 

 oblong obtuse pinnules and conspicuous yellow eventually 

 reddish-brown naked sori. It flourishes best on stumps of trees, 

 etc., by the side of brooks or moist places, but it may frequently 

 be seen on old walls, etc. The variety Cdmbricum has the 

 pinnules finely divided. 



2. P. Dryopteris. Oak Fern. An elegant species with 

 slender creeping rootstocks and alternate bipinnate deltoid 

 membranous fronds of a pale green colour, rarely more than 6 

 to 9 inches high. Stipes slender, scaly at the base. Frond 

 divided into three nearly equal branches, forming a triangle ; 

 pinnules obtuse, obscurely toothed. This is found in shady 

 mountainous districts in Britain, and is widely distributed in 

 the northern hemisphere. 



P. Robertianum, syn. P. calcareum, is very near the last, 

 and perhaps only a variety of it. The fronds are more 

 coriaceous and glandular, and the lateral branches of the frond 

 are smaller than the central one. It is a rare Fern in Britain, 

 growing on limestone rocks. 



3. P. Phegopteris. Beech Fern. A delicate small-growing 

 species with pale-green pinnate triangular fronds from 6 

 inches to a foot high. Pinnae pinnatifid, the lower pair much 

 smaller than the others and deflexed. Pinnules obtuse, ciliate ; 

 stipes very slender and brittle, exceeding the leafy portion of 

 the frond, slightly scaly at the base. Moist shady woods and 

 rocks throughout Britain. Distribution general in the north 

 temperate zone. 



4. P. alpestre, syn. Pseudathyrium alpestre. This is 

 strictly an alpine species, resembling the Lady Fern in general 

 appearance. It has a stout rhizome and lanceolate bipinnate 

 fronds varying from 6 inches to 2 or even 3 feet in height. 

 Pinnae pinnatifid; pinnules toothed. Stipes 4 to 6 inches 

 high, scaly at the base. Sori arranged in a single row on each 

 side of the midrib. In Britain only on the lofty mountains of 

 Scotland, and in arctic and alpine Europe, North America, 

 and Western Asia. 



P. flexile or Tiumile is a variety with looser narrower fronds, 

 and more distant deflexed pinnae. 



