CHARACTERS OF TRIBES AND GENERA. 233 



distributed, in both temperate and tropical regions, vary- 

 ing much in size and circumscription of the fronds, and in 

 the position of the sori being terminal or lateral on the 

 venules, which, although common to closely allied species, 

 has however, been considered by many authors suflBoient 

 to characterise several genera. The most obvious differen- 

 tial character of species consists in some having erect 

 vernation and the others decumbent, which admits of their 

 being arranged in groups as follows : — 



Group 1. — ■VeniaUon erect, acaulose or subarhoroid 



{Desmopohiu7n) . 



* Fronds pinnate, pinnt:e entire or piniiatifid: 



Sp. P. hasttefolia (Sm>.) (v v.) ; P. elongata {IVall.) ; P. 



Walkerae (Hook.) (v v.) ; P. Sieljeriana (Kaulf.) (v v.) ; 



P. appeudiculata (Wall.) ; P. auriculata {Wall); Bedd. F. 



Brit. Ind., pi. 203 ; P. erubescens {Walt.) ; Bedd. F. Brit. 



lad., pi. 213 ; P. Tijucana (Badd.) ; P. Imrayana, /. Sm. 



{Nephrodium, Mooli.) ; P. rotundata {Willd.); P. flavo- 



punctata (JyauJf.) ; P. rude (Kze.) ; P. decassata, {Linn.) 



(v V.) ; P. caudata (Kaulf.) 



** Froiida Tjl-tripianate, midlifid. 

 P. drepana {S'lv.) (v v.) ; P. platyphyllum {Rook.) ; P. 

 rufescens ( Wall.) (v v.) ; P. grande {Pr.) ; P. ampla(7/. B. K.) 

 (v V.) ; P. spectabilis {Kaulf.) (v v. ) ; P. lachnopoda (J. 8m.) 

 (v V.) ; P. macroptera (Kaidf.) (v v.) ; P. macrophylla 

 {TIoolc.) ; P. molle {Bo.i-h.) {Bohjpiodium Bianece, Hook.) 



Group 2. — Vernation decumlent (Catapodium). 

 P. alpestris {Hopipie) (v v.) ; P. flexilis (Moore) (v v.) ; 

 P. brunea ( TVall.) ; P. paludosa (Bl.) ; P. divergens ( Willd.) 

 (v V.) ; P. effusa (Sw.) (v v.) ; P. triohodes (Beinw.) (v v.) ; 

 P. rugulosa (Labill.) (v v.) ; P. unidentata (Hook.) (v v.) ; 

 P. ornata (Wall.). 



