SMOOTH THEEE-BEANCHED POLYPODY 

 OB OAK FEBN. 



Polypodiwn Dryopteris.* LINNAEUS. 



This, the smallest of the Polypodies, is also one of the 

 most delicate of all British Ferns : very easily recog- 

 nizable by its smooth fronds, of a bright lively green, 

 divided into three branches, the last characteristic 

 even more obvious in the young fronds, which are 

 rolled up in little balls at the ends of their three slender 

 stalklets. Its height is generally not more than six 

 inches, often less, but it sometimes grows to twelve or 

 fourteen. It is fragile, produced about April, and in 

 succession throughout the summer, soon withered by 

 heat or drought, and at once destroyed by frost. The 

 fronds rise from a slender creeping stem, which often 

 forms densely matted roots. The stipes is usually 

 much longer than the leafy part, thin, brittle, and dark 

 coloured. The general outline is five-sided, owing to 

 the division of the fronds into three triangular branches. 

 One of the peculiarities of the Oak Fern is the deflection 

 of the rachis (or midrib) at the point where the 

 branches take their rise ; and another (of less botan- 



* Also Polystichum Dryoptcris, Lastrea Dryopteris, &c. 



