88 WAYSIDE AND WOODLAND FERNS. 



downiness of the frond is seen to be due to the presence of 

 an incalculable host of minute stalked glands, which extend 

 also to the stipes and rachis, and give a greyish mealy effect to 

 the dull green frond. In addition, the frond is of more erect 

 growth, more stiff and rigid, and of the three principal divisions 

 the lateral ones are proportionally smaller to the central part. 

 The sori and their arrangement are similar to what we find in 

 P. dryopteris ; and the spores are mature from June to August. 



The name robertianum is borrowed from Herb Robert 

 (Geranium robertianum), on account of a resemblance between 

 the unpleasant odour of each. 



The distribution of the Limestone Polypody extends south- 

 wards from Cumberland to Derbyshire and Glamorganshire ; 

 also in Somersetshire, Wiltshire, and Gloucestershire. It is not 

 found in either Scotland or Ireland. In Europe it occurs in 

 France, Switzerland, Germany, Hungary, and Norway. Farther 

 afield it is found in the Himalaya and North America. 



Alpine Polypody (Polypodium alpestre}. 



The position and, consequently, the designation of this species 

 has been the subject of controversy ever since its distinctness 

 as a species was established. The point is, should it be 

 considered as the Alpine Lady-fern or the Alpine Polypody ; 

 as Asplenium alpestre or Polypodium alpestre ? The authorities 

 are divided. In habit of growth, and general appearance of 

 the frond, no one would hesitate to say it was a Lady Fern 

 variety or other near relation. But then, the Lady Fern has its 

 sorus covered by an oblong kidney-shaped indusium. This fern 

 has no indusium at all, although at rare intervals it produces 

 what has been regarded as a false indusium, as it is only found 

 in connection with imperfect sori. And so, for want of an 

 indusium, it has been placed among the Polypodies, with which 

 it agrees in having circular sori. There the matter stands for 



