GENERA OF BllITISII FERNS. 51 



into a special indusium. It contains the gemis 

 Pteris. 



11. Pteris = Dorsal-fruited Ferns, having the spore-cases 



in a continuous line at the edge of the frond, beneath 

 indusia, formed of the altered margin. 



§ ADIAHTE^ = Ferns the marffin of u'hose fronds 

 bears reflexcd lobes, which are changed to indusia, 

 and hear the spore-cases on their under surface. It 

 contains the genus Adiantum. 



12. Adiantum = Dorsal-fruited Ferns, having the spore- 



cases in patches, on the reflexcd, altered apices of 

 the lobes of the fronds, which form indusia. 



§ CYSTOPTERIDEJE = i^t^r;^ A- ichose sori have spe- 

 cial ovate indusia affixed behind, and infected hood- 

 like over them. It contains the genus Cystopteris. 



13. Cystopteris = Dorsal-fruited Ferns, having cucullatc 



or hooded scmi-involucriform indusia, attached by 

 their broad base. 



§ PERANEMEiE = Ferns ichose sori have special 

 involucriform or semi-involucriform indusia, round- 

 ish, and springing from the hack of the veins It 

 contains the genus Woodsia. 



j: 2 



