volucre very broad ; at lon^tli HattciUMl out, exposing tlie now 

 confluent son. Sterile and fertile fronds unlike ; stalk light- 

 colored. 



7. Ptkkis. Sporangia borne on a continuous, vein-like, mar- 

 ginal receptacle, which connects the ends of the veins. Invohure 

 continuous around the pinnies; stalk light-colored. 



8. Adiantum. Sj)orangia borne at the ends of the veins, on 

 the under side of the reflexed and membranous margin of the 

 frond. ]\lid-vein of the pinnies mostly eccentric or dissipated into 

 forking -veinlets. Stalk dark-colored. 



TRIBE IV, BLECIINE^. Indusium a special membrane 

 usually concave or arched over the sorus, and opened at maturity 

 alonsj the inner edire. Sori more or less cloncjated, borne on a 

 veinlet or a special receptacle parallel to the midrib. Two genera. 



9. LoMARiA. Sori continuous from the bast* of the pinna to 

 its apex. Sterile and fertile fronds unlike. Veins free. 



10. AVoODAVARDiA. Sori interrupted, forming a chain-like row 

 each side of the mid-rib. Fronds all alike, and, in our species, 

 very large. Veins reticulated. 



TRIBE V, ASPLENIE^. Sori more or less elongated, 

 borne on veins oblicpie to the mid-rib, covered by a special, usually 

 flattened indusium. Indusium attached to the fertile veinlet by 

 the outer edge. Only one genus. 



11. AsPLENiUM. The only genus represented. 



TRIBE VI, ASPIDIE^. Sori orbicular, or roundish, on the 

 back, or sometimes on the tip of the fertile veinlets, (naked in 

 I?hego|iteris,) provided with a s})ecial indusium, -which is variously 

 shaped. Four genera. 



12. PiiEGOPTERis. Indusium wanting. Sori very small, dot- 

 like, borne on the back of the fruiting veinlets. 



13. AspiDiUM. Indusium orbicular or reniform. Sori borno 

 on the backs or at the tii)S of the veinlets. 



14. Cystopteris. Indusium convex, spoon-shajjed, fixed across 

 the fertile veinlet, below the sori, reflexing as the fruit ripens. 



15. WooDsiA. Indusium globular, placed beneath the sorus, 

 and at first enveloping it, then sj)litting into segments, and turn- 

 ing back. 



