94 CHARACTERS OP TRIBES AND GENERA. 



areoles ; the costal areoles always vacant. Receptacles 

 punctiform on the combined apices of the excurrent vein- 

 lets. Sori round, transversely one to two serial, naked. 



Type. Polypodium aureum, Linn. 



Illust. Hook, and Bauer, t., 112. Moore Ind. Fil., p. 58, 

 figs. 13. J. Sm. Ferns. Brit, and For, fig. 9. Hook. 

 Syn. Fil., t, 5, fig. '48, g. 



OBS. This is a well-marked genus, containing about 

 half a dozen species, all natives, of the West Indies and 

 Tropical America. In general habit it resembles Gonio- 

 phlel)ium, but is distinguished by the sori being borne on 

 the combined apices of at least two excurrent veinlets, and 

 by the costal aeroles having no free veinlet. 



Ex. P. aureum (Linn.\(v v.), P. sporodocarpum ( Willd.}, 

 (vv.), P. areolatum (Willd.\ (v v.), P. pulvinatum (Lirili), 

 (v v.), P. decumanum (Willd.\ P. dictyocallis (Pee), (v v.). 



Sect. 3. PLEURIDE^E. 



12. PLEURIDIUM, Presl (1836). 

 Polypodium, Sp. aufh. y Hook. Sp. Fil. ; Phymatodes, section 



Pleuridium, Presl in part. 



Surculum short, or elongating. Fronds simple, rigid, 

 papyraceous, or coriaceous, from 6 inches to 2 feet in 

 length, thick marginate. Primary veins costeeform, elevated, 

 straight. Venules compound anastomosing. Receptacles 

 compital, punctiform. Sori round or oblong, obliquely one 

 or two serial between the primary veins. 

 Type. Polypodium crassifolium, Linn. 

 Illust. Schott. Gen. Fil. t. 1 (Anexetum). Hook, and 

 Bauer, Gen. Fil., t. 29. J. Sm. Ferns, Brit, and For., 

 fig. 22. 

 OBS. Presl arranges the species of Pliymatodes under 



