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. 
§ ADIATTTEiE = Ferns the margin of whose fronds 
hears reflexed 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 reflexed, altered apices of 
the lobes of the fronds, which form indusia. 
§ CYSTOPTERIDEiE = Ferns whose sori hare spe¬ 
cial ovate indusia affixed behind, and inflected hood- 
like over them. It contains the genus Cystopteris. 
13. Cystopteris — Dorsal-fruited Ferns, having cucullate 
or hooded semi-involucriform indusia, attached by 
their broad base. 
§ PERANEMEiE = Ferns whose sori have special 
involucriform or semi-involucriform indusia, round¬ 
ish, and springing from the hack of the veins It 
contains the genus Woodsia. 
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