THE POLYPODIES. 
329 
4 . 
THE LIMESTONE POLYPODY. 
Polypoclium calcareum. 
Plate 2, Pig. 4. 
ABLER, darker in hue, 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, it 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 very dis- 
ts 
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 
