78 HISTORY OF BRITISn FERNS. 



in Scotland it is distributed pretty generally ; it is very 

 rare in Ireland. 



This species has been called Polysticlium Dryopteris, 

 Lastrea Dryopteris, Phegopteris Dryopteris, and Gymno- 

 carpium Dryopteris. 



Polypoditun Robertiamiin, Hoffman. 

 The Limestone Polypody. (Plate III. %. 1.) 



This Fern is known from P. Dryopteris — to which it 

 is so nearly related that some botanists do not consider it 

 distinct — by having its fronds less decidedly, though some- 

 what three-branched, and by having its surface covered 

 with small stalked glands, which give a mealy appearance 

 to every part. In addition to these points of difference, 

 the fronds in this species are of a dull deep green, more 

 rigid, and without the marked deflection of the rachis so 

 obvious in P. Dryopteris. The young fronds, moreover, 

 instead of being rolled up in three little balls, have their 

 pinnffi all rolled up separately. The glandular surface of 

 the frond is very readily seen with a good pocket lens, 

 which is a very necessary aid to the study of Ferns. 



The Limestone Polypody grows from six inches to a foot 

 in height. The fronds are nearly triangular, with the 



