THE POLYPODIES. 
331 
The Limestone Polypody has not a wide distri¬ 
bution. It occurs in localities iu the north of 
England, and is found in some parts of the West 
and in Wales. But from Scotland and Ireland 
it is almost entirely absent. It is, however, not 
an uncommon Fern in the limestone districts 
where it grows. 
It is very much hardier in its constitution than 
' the Oak Fern, and will sometimes thrive well 
when placed on the sunny or exposed part of a 
rockery, or in the most sunny part of a green¬ 
house. The soil which suits the other Polypodies 
will suit Polyjoodium calcareum. But from its 
fondness for limestone it will be supposed that the 
presence of limestone in the soil is desirable. In 
cultivation, therefore, small pieces of limestone 
should be mixed with the soil in which it is 
grown. Like all the Polypodies it has a creeping 
rhizoma, which travels half under the surface of 
the ground, its matted fibrous roots finding their 
way into the lower depths of the soil in which it 
grows, whilst from its upper surface grow the 
clusters of dark bluish-green fronds. 
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