196 THE POLYPODIES. 
ultimately be included in this family notwithstanding 
the absence of the indusium. For our present purpose 
we shall include them with the other non-indusiate 
forms, 
The Common Polypody. 
Wherever there isa shaded ledge of 
rocks inthe northeastern States one is 
almost sure to find the polypody (Poly- 
podium vulgare). Thereis no question 
as tochoice of location with this sturdy 
species. All are alike to it, provided 
there are rocks upon which it can grow. 
The only preference it has is for the 
tops and upper shelves of the rocks 
where the soil is moderately dry. So 
characteristic is it in such situations 
that when one sees a fern clad rocky 
summit from a distance too great to 
discern the individual fronds he identi- 
fies them with confidence as this spe- 
cies. 
The fronds of the polypody are thick 
and leathery and remain green all 
winter. They grow from a slender, 
brown-scaly, branching rootstock that 
creeps at the surface of the soil, and 
are produced during most of the early 
summer. They are ordinarily about a 
foot long with a short slender stipe and 
narrow pinnatifid or pinnate blade. 
The pinnules are linear, usually blunt at the ends, and 
COMMON 
POLYPODY. 
Polypodium vulgare. 
