POLYPODIACEAE. 



417 



2. POLYPODIUM [Tourn.] L. 



Pinnate or simple ferns with stipes articulated to the creeping rootstocks. 

 Sori hemispheric, dorsal, in one or more rows on either side of the midribs. 

 Indusium none. Sporanges pedicelled, provided with a vertical ring which 

 bursts transversely. Veins free or variously anastomosing. [Greek, in allu- 

 sion to the knob-like prominences on the rootstocks of some species.] About 

 350 species, of wide distribution, mostly tropical. Type species: Polypodium 

 vulgare L. 



1. Polypodium Plumula H.B.K. 

 PLUME POLYPODY. (Fig. 452.) Leaves 

 erect or spreading; petioles l'-4' long, 

 black, slender; blades narrowly lanceo- 

 late, 8'-16' long; pinnae numerous, 

 narrow, entire, blunt, the lower abruptly 

 smaller, the surfaces naked except the 

 black wiry rachis; veins once forked, 

 obscure. [P. elasticum A. Eich. ; P. 

 pectinatum of Jones.] 



Shaded holes and crevices between 

 Harrington Sound and Castle Harbor. Na- 

 tive. Florida and the West Indies. 



Polypodium pectinatum L., a similar Floridian and tropical American 

 species, is recorded as Bermudan by Kein, and by Hemsley from Walsingham, 

 but subsequent collectors have failed to find it in Bermuda. It differs by 

 being usually larger and in having veins 2-3-forked. 



3. PYCNODORIA Presl. 



Mostly large ferns, the petioles not jointed with the rootstocks, the leaves 

 variously divided. Sori marginal, continuous or nearly so, on a filiform or 

 narrow receptacle connecting the tips of the free veins ; indusium simple, 

 membranous, formed by the reflexed margin of the leaf. Sporanges pedicelled, 

 provided with a vertical ring which bursts transversely. [Greek, thick- 

 skinned.] Many species, of warm and tropical regions. Type species: Pteris 

 opaca J. Smith. 



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