13 . 
THE COMMON POLYPODY. 
Poltj podium vulgare. 
Plate 7, Figs. 1 and 2, Page 253. 
There are five species of Polypody in the British Islands, 
and they form an interesting little group, alike in the 
peculiarity which is the character of the genus Polypodium, 
hut differing from one another in some important respects. 
The characteristic of the genus Polypodium consists in the 
fact that the little heaps of spore cases on the hacks of the 
fronds are absolutely uncovered by any protecting membrane 
or indusium. Polyp odium is derived from two Greek words ; 
ptolys ‘ many,’ and pous ‘ a foot,’ and freely rendered, means 
1 many footed’ — the designation referring to the creeping and 
branching rhizomas from which the fronds of these Ferns 
spring, giving to some extent the idea of feet. 
Polypodium vulgare, though in respect to the characters 
just indicated, resembling all the British species of its genus, 
differs from them, not only in form but in its habitats. It 
grows in a great variety of places, and in situations in which 
the other British Polypodies are never found. Its creeping 
rhizoma delights to revel amidst soft rich leaf-mould collected 
in places at almost every kind of elevation above the 
ground level. In forests vast numbers grow in pollard 
trunks, and in the forks of other trees, or close to the ground 
— though just raised above it — upon the decaying stumps of 
trees which have been felled. Numbers of these plants also 
