204 THE POLYPODIES. 



longest on the lower side. 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 Robertiand] 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." 

 Phegopteris means literally beech fern. As the latter 

 genus is defined at present, it contains nearly a hundred 

 species. 



