KEY TO THE GENERA OF FERNS 149 



Fruit-dots small, near the 7nargin. Fronds delicate, trian- 

 gular in outline; in one species, temate. 



rhcgopteris, p. 7. 



2. Fertile fronds differing in form from the ster- 



ile, OR sometimes only partly fertile. 



With indusium. 



Fruit-dots ohlong or linear, in chain-like double rows par- 

 allel with the midribs. Indusium fixed by its outer margin 

 and opening on the inner side. Veins more or less netted. 

 In one species the fertile frond is unUke the sterile. 



IVoodwardia, p. 43. 



Sporangia ovate, in double rows on panicled, contracted 

 pinnules at the summit of the frond. Indusia thin, imbri- 

 cated, scale4ike, and fixed to short, obUque veinlets. Sterile 

 pinnules evergreen, palmate, in alternate pairs on a twining, 

 wireJike stem. Lygodiuin, p. 79. 



Without indusium. 



Sporangia /rz?JzV/(r(/. The fertile fronds vary in the differ- 

 ent species. In one, the entire frond is fertile : in others, the 

 middle portion of the frond, or the tip is fertile. The fertile 

 pinnae or fronds are very much contracted, bearing the green 

 sporangia on the margins of the minute divisions. Fronds 

 large and clustered. OsvitLnda, p. 48. 



3. Entire fronds fertile and wholly unlike the 



sterile ones. 



\A?ith indusium. 



Sporangia inclosed in berry-like divisions of the fertile 

 fronds which are twice pinnate, much contracted, and very 

 different from the sterile ones. Indusium very delicate and 

 obscure. Sterile fronds sometimes very large. 



Onoelea, p. 57. 



