THE LIMESTONE POLYPODY. 
Polypodium calcareum.* Smith. 
The Limestone Polypody differs from the Oak Fern 
in its stouter, erecter, and more rigid habit, and in 
the mealy-looking gland ulosity of its surface; yet 
still more in that the division of its fronds is pinnate 
rather than into three distinct branches. The fronds 
are also of a duller and deeper green, and without the 
marked deflection of the rachis. And instead of the 
branches being rolled up into three balls, the young 
pinnae curl in on their rachides and the entire frond 
upon its rachis, so that the frond is of the ordinary 
bipinnate structure. Its fronds, including the stipes, 
vary from six to eighteen inches in height: their 
form is triangular with a tendency to the pentagonal 
appearance of the Oak Fern, because of the larger 
size of the two lower pinnae. These lower pinnae 
are pinnate, with pinnatifid pinnules again pinnate 
and the upper pinnatifid. The fructification is scat¬ 
tered over the whole dorsal surface of the frond ; 
* Also P. Robertianum, P. Dryopteris, Lastrea calcarea, 
Lastrea Robertianum, Phegopteris calcarea, &c. 
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