THE POLYPODIES, 



4. 



THE LIMESTONE POLYPODY. 



Polypodium calcareum. 



PLATE 2, FIG. 4. 



JALLER, darker in line, and hardier than 

 its relative the Oak Fern, is the Lime- 

 stone Polypody. From a height of six 

 inches to a foot, and sometimes more, ifc grows, 

 generally preferring a limestone soil ; and hence 

 its name. The frond differs from that of the Oak 

 Fern in not having the same arrangement of three 

 distinct branches. Its colour, too, is verv dis- 

 tinct, being a dark green, having, as we venture 

 to think, a decidedly bluish tinge. The stem is 

 usually about the same length as the leafy por- 

 tion of the frond. The shape of the latter is 

 triangular. The pair of branches at its base are 

 considerably larger than the pair above it. The 

 four branches are attached to the rachis, each by 

 a short stem. But the branches or rather they 

 should be termed in this case the leaflets above 



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