204 THE POLYPODIES. 
longest on the lowerside. Even in unfurling, the blades 
show their ternate character, each division being rolled 
up separately. These three little green balls on their 
slender thread-like stalks are exact miniatures of the 
conventional sign of the pawnbroker. The ultimate 
segments are often slightly toothed and the rather in- 
conspicuous sori are borne near their margins. 
A form of the oak fern, often called the limestone poly- 
pody (Phegopteris Dryopteris Robertiana) is occasional 
in Canada and the northwestern United States. It is 
distinguished by its larger size, glandular fronds, greater 
rigidity, and in having the lower pinnules on the lateral 
divisions of the frond scarcely longer than the others. 
It is frequently considered to be a distinct species and 
named P. calcarea, but the opinion of the majority places 
it as a variety of the common form. 
The oak fern is found from Virginia, Kansas and Col- 
orado to the far North and also in Europe and Asia. 
The variety is also found in the Old World. The plant 
is a lover of moist and rocky woods and makes an excel- 
lent species for cultivating at the base of the artificial 
rockery. The initial for this chapter shows a frond of 
this fern. 
The name Polypodium is from the Greek and means 
many feet. By some, this is conjectured to be in allusion 
to the branching rootstocks of certain species, but it 
seems quite as likely to refer to the numerous roots 
which nearly all produce. One writer observes of our 
common species that “ the rhizome when destitute of the 
fronds has the appearance of some kind of sea polypus.” 
Phegopterts means literally beech fern. As the latter 
genus is defined at present, it contains nearly a hundred 
species. 
