POLYPODIES. 



51 



LIMESTONE POLYPODY.* 



This Polypody and the Oak Pern differ from all other 

 British Polypodies, in the fronds being divided into three 

 parts or branches. In the present fern the lower branches 

 are not equal in size to the upper, whilst in the Oak Fern 

 the three branches are nearly equal. The fronds of the 

 Limestone Polypody are nearly triangular in form, borne 

 on rigid foot- stalks. The branches are pinnate, or divided 

 to the centre into segments, of which the lower branches 

 have the segments again deeply cut or divided, and the 

 upper nearly entire. The whole surface of the frond has 

 a mealy appearance. The sori are near the margin on the 

 under surface. It has been called the Limestone Polypody 

 on account of its predilection for calcareous soils, to which 

 it appears to be confined ; hence it is very local in its 

 distribution. In the rocky parts of Derbyshire it is not 

 uncommon ; but is not confined to that county, since it 

 has been found in more northern and western districts of 

 England. Dr. Hooker found it in India on the Hima- 

 layan Mountains at from 5,000 to 8,000 feet elevation, 

 and it is also an inhabitant of the United States of North 

 America. It is hardy, and better for outdoor cultivation 

 than the Oak Fern, not requiring much moisture. A 

 calcareous soil is not essential, though some growers mix 

 old mortar with the compost. (Plate IL, fig. 3.) 



THE PAESLUY FEENS, 



Clusters of spore-cases at first circular, then spreading-, nailed; edges of 

 fertile fronds bent back. 



It is perhaps scarcely applicable or correct to call this 

 the genus of Parsley Ferns, on account of our solitary 

 British species ; but as far as that species is concerned, 

 it is preferable to calling them Rock Brakes. This grou p 

 is named by botanists Allosorits, from two Greek words 



Polypodium Rohertianum, Hopf. 



