72 POLYPODIUM. 



PHLEBODIUM. R. Brown. 



The veins are pinnate or branched, the venules arcuately or 

 angularly anastomosing, forming on their angular meetings or 

 exterior side two veinlets, which are sporangiferous where the 

 two veinlets join. 



Sori round or oval, transversely uniserial, or multiserial. 



Differing from Gonioplilebium by having the lower venules 

 combined, the sori being formed at the apex or point of junction. 



DRYNARIA. BoRY. 



The veins are mostly costoeform, parallel, or flexuose ; venules 

 compound anastomosing. 



The sporangia is produced on the angles or points of con- 

 fluence of numerous veinlets. 



Sori circular or oblong; transversely uniserial, or in one or 

 two oblique rows between each pair of primary veins, or irre- 

 gular. Sori forming protuberances on the upper or superior 

 side of the frond. 



The frond smooth and thick. 



Differing from Plilehodiutn by the venation being more com- 

 pound, and by the sori being situated where a number of 

 venules join. 



The British representatives of this genus are Polypodium vul- 

 gar e, P. phegopteris, P. alpestre, P. dryopteris, and P. calcareum- 

 Perhaps the North American P. hexagonopterum of Michaux 

 may eventually be added to this list. 



