20 BRITISH FERNS. 



indusia, attached by their concave side, the detached 

 side fringed with hair-like segments. 



7. Asplenium=lL>orsal-fmite(i Ferns, having the indusia 



straight and elongate, and attached by the side to- 

 wards the margin of the pinnae or pinnules. 



8. Scolopendrium=DoT&a.l-frmted Ferns, haying the sori 



elongate, and proximate in parallel pairs, the indusia 

 opening along the centre of the twin sori. 



9. Ceterctch = Dorsal-fruited Ferns, having the indusia 



obsolete, and the sori hidden among densely imbri- 

 cated, rust-coloured, chaffy scales. 



BLECHNEjEz^-Z^enw whose sori have special indusia, form- 

 ing longitudinal lines between the midrib and margins 

 of the leaflets or divisions of the frond. 



10. j5ecAwMm=Dorsal-fruited Ferns, having the spore-cases 



in a continuous line between the midrib and margin 

 of the divisions of the frond, covered by linear 

 indusia. 



PTERJDEJE = Ferns^ the margin of whose frond is sori- 

 ferous, and continuously or interruptedly changed into 

 a special indusium, 



11. P&?'is=I)orsal-fruited Ferns, having the spore-cases in a 



continuous line at the edge of the frond, beneath 

 indusia, formed of the altered margin. 

 ADiANiEM=Ferns, the margin of whose fronds bears re- 

 flexed lobes, which are changed to indusia, and bear 

 t/te spore cases on tlieir under surface. 



12. .4(&'<mfem=: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 have special ovale 

 indusia affixed behind tJie sori, and inflected hood-like 

 over them. 



13. Cystopteris = Dorsal-fruited Ferns, having cucullate or 



hooded semi-involucriform indusia, attached by 

 their broad base. 



WooDSTEM=Ferns whose^ sori have special involucriform 

 or semi-involucriform indusia, roundish, and springing 

 from the back of the veins. 



14. TFoocfcia=Dprsal-fruited Ferns, having the indusia 



involucriform, i.e., attached beneath the sori, and di- 

 vided at the margin into hair-like incurved segments. 

 HYMENOPHYLLE^E = Ferns whose sori are produced 

 around the ends of veins projecting from the margin, 



