34 
THE LIMESTONE POLYPODY. 
the sori are small and ronnd, consisting of nnmerons 
crowded spore-cases, entirely without indnsia, arranged 
in linear sub-marginal series along each side of the 
lobules, or in series between the midrib and margin 
when the lobules are but slightly developed,— often 
more or less confluent. Spore-cases pale brown, 
roundish obovate, small and numerous. Spores 
ovate or oblong, somewhat granular. 
The Limestone Polypody, as its name infers, is 
found usually on exposed rocky limestone tracts: 
growing there very abundantly. In cultivation, how¬ 
ever, a limestone soil is not essential to its well-being. 
Like the generality of Perns, it requires good drainage, 
but bears the sun more than others. It grows al- 
almost throughout Europe, in Canada, and the United 
States of America; and has been gathered by Dr. 
Hooker and Dr. Thomson on the Himalaya Mountains 
at the elevation of 6,000 feet. 
Habitats. 
Scale Force (J. Robson), Whitbarrow, Hewbiggin 
Woods, Gilt Quarries, Baron Heath, Arnside Knott, 
Hutton Hoof Crags, Farleton Knott, Caskill Kirk, &c. 
Only one variety: 
variabile, — Whitbarrow, J. M. Barnes and F. Clowes. 
