38 WHERE TO FIND FERNS. 



pinnae in pairs or alternate upon the rachis ; lowest pair 

 of pinnae somewhat narrowly triangular, pinnate and 

 sometimes bipinnate at their bases, and divided into 

 opposite or alternate, oblong, and somewhat cone-shaped 

 pinnules, which are more or less deeply cleft into narrow, 

 oblong, blunt-pointed lobes. The succeeding and upper 

 pairs of pinnae are less and less divided, on the same 

 principle, as they near the apex of the frond, the divi- 

 sions of the several pinnae being similarly less and less 

 towards their apices. This principle of gradation is 

 always observed in all ferns the divisions or indenta- 

 tions of all the parts of fronds being less and less from 

 base to apex of frond, pinna, pinnule, lobe, or serrature. 

 As in Polypodium dryopteris, the lower pairs of pinnae 

 have their lower pinnules longer and more developed 

 than those on the upper sides of their respective 

 secondary rachides. Fructification marginal on the lobes 

 or pinnules according to the size and development of 

 the pinnae and bearing a strong general resemblance to 

 the arrangement of the fructification of the Bracken. 

 But in Polypodium calcareum the sporangia are non- 

 indusiate. The fructification is spread equally over the 

 whole under surface of the frond, the pinnules of which 

 are concave on their under sides, giving to them a curled, 

 crisped appearance. 



HABITATS. Limestone districts, in moist crevices of 

 limestone rocks and amongst loose limestones. It 

 prefers shady positions especially for its roots, but it 

 will oftentimes be found growing in places that arc 

 somewhat sunny. 



WHERE FOUND. In England, in the counties of 

 Bucks, Cumberland, Derby, Durham, Gloucester, Here- 

 ford, Lancaster, Oxford, Salop, Somerset, Stafford, 

 Westmoreland, Wilts, Worcester, and York. In Wales, 

 in the counties of Brecknock, Caernarvon, Denbigh, and 

 Glamorgan. In Scotland, it is said to have been found 

 growing wild in the counties of Aberdeen and Perth, 



