GENERA OF BRITISH EERXS. 49 



1. Polypodiuni= Dorsal -fruited Ferns, with the circular 



sori exposed, i. e. -without covers. 



2. AUosorus = Dorsal-fruited Ferns, ^Yith the roundish 



sori becomino; laterally confluent beneath the re- 

 flexed, unaltered margins of the frond. 



§ GYMNOG-RAMMEjE = Ferns icJiose linear clusters 

 of spore-cases have no special covers. It contains 

 the genus Gymnogramma. 

 S. Gymnogramma = Dorsal-fruited Ferns, having the sori 

 linear, forked, naked. 



§ ASPIDIEJE = Ferns ti-hose sori hate sptecial indusia, 

 of a circular or roundish form, and springing here 

 and there, from the back of the veins. It contains 

 the genera Lastrea and Polystichum. 



4. Polystichum = Dorsal-fruited Ferns, having circular 



umbilicate indusia, attached by their centre. 



5. Lastrea =^ Dorsal-fruited Ferns, having reniform indu- 



sia, attached by their indented side. 



§ ASPLENIEJE =i^fr;25 whose sori hate special in- 

 dusia, of an oblong or elongated form, and springing 

 from the sides of the veins. It contains the genera 

 Athyrium, Asplenium, Ceterach, and Scolopendrium. 



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