GENERA OF BRITISH FERNS. 
51 
into a special indusium. It contains the genus 
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. 
§ ADIAT^'TE^ = Ferns the margin of whose fronds 
bears reflexed lobes, which are changed to indusia, 
and bear 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 reflexed, altered apices of 
the lobes of the fronds, which form indusia. 
§ CYSTOPTERIDE^ = Ferns whose sori hare spe- 
cial orate indusia ajfixed behind, and inflected hood- 
like orer them. It contains the genus Cystopteris. 
13. Cystopteris = Dorsal-fruited Ferns, having cucullate 
or hooded semi-involucriform indusia, attached by 
their broad base. 
§ PERANEMEiE = whose sori hare special 
inrolucriform or semi-inrolucriform indusia, round- 
ish, and springing from the back of the reins It 
contains the genus Woodsia. 
K 2 
