THE POLYPODIES. 197 
broaden somewhat as they join the rachis. Occasionally 
they are slightly serrate. It sometimes happens that 
fronds of this species are mistaken by the novice for 
those of the Christmas fern which are also pinnate, but 
the latter may always be distinguished by the eared 
pinnules. 
About the middle of June the bright yellow-brown 
sori begin to appear. They are found on the backs of 
ordinary fronds in a double row near the margins of the 
pinnules and mostly in the upper two thirds of the frond. 
They are round, very regular in arrangement and so 
large as to be quite conspicuous, looking like little buttons. 
Except the narrow-leaved chain fern, none of our species 
produce sori so large. There is no indusium. 
Among its common names are adder’s fern, golden 
polypody, golden-locks, moss fern, stone fern, stone 
brake and wall fern. Most of these are of obvious deri- 
vation. It was once considered valuable as a pectoral 
and, boiled with sugar, was a remedy for the whooping 
cough. Little, if any, use is made of it at present. Ac- 
cording to some authorities, this is the original oak fern 
although Phegopteris Dryopteris now has the title. 
The polypody has numerous varieties but few of them 
are worthy of special note. The most famous is the 
Welsh polypody which has a frond much broader than 
the normal with the pinne cut nearly to the midrib 
into narrow segments making a bipinnatifid frond. It 
is called the variety Cambricum, and is supposed to be 
always sterile. It was originally found in Wales and has 
seldom been noted in this country but is likely to occur 
in any locality where the type is common. The other 
varieties reported are amgustum with narrow serrate pin- 
nules, rotundatum with short, round-ended pinnules and 
