BEITISH AND EXOTIC. 



POLYPODIACEiE. R. Beown. 



This very interesting division of Ferns liave the sj)orangia, 

 which are more or less transparent, of an oval or round form. 

 The sporangia are all unilocular and pedicellate. Sometimes, 

 but very seldom, they are sessile. 



The opening of the seed vessels runs transversely, and the 

 sporangia, in the greatest number, are supplied v/ith an elastic 

 ring, which surrounds them vertically, and is articulated, 

 (jointed.) In a few examples, this ring instead of being- 

 vertical, is found to be oblique. 



TEIBE I. 



GYMNOGRAMMA. Desvaux. 



This tribe takes its name from the circumstance that the 

 linear sori are not furnished with an indusiura, and are there- 

 fore naked. The derivation of the word Gymno gramma being 

 from the Greek gymnos — naked, and gramma — writing. 



The veins in the frond are branched, and their apices are 



