GENERA OP BRITISH FERNS. 13 



CHAPTEK IIL 



TABULAR ARRANGEMENT OP THE BRITISH PERNS GENEKA 

 SPECIES VARIETIES. 



THE Ferns, it will be recollected, are flowerlcss plants, 

 bearing seed-vessels (spore-cases) on their leaves (fronds), 

 and these spore-cases are placed either on the back of the 

 frond (dorsal) or on their margins (marginal). The British 

 Ferns belong to groups which are called Polypodiaccce, 

 Osmundacece, and Ophioglossacecc. 



L POLYPODIACE^E. This group consists of Ferns having 

 the leaves rolled up in a circinate or crosier-like 

 manner while young ; and the spore-cases girt with an 

 elastic ring, and bursting by an irregular transverse 

 cleft. It comprises several lesser groups or sections 

 called Polypodiece, Gymnogrammece, Aspidiece, Aspleniece, 

 Blechneos, Pteiidece, Adiantece, Cystopteridece, Woodsiece, 

 and Hymenophyllece. 



PoLYPODiEM=Ferns whose round dusters of spore-cases 

 have no special membranous cover (indusium). 



1. Polypodium='Dor:$al-fraited Ferns, with the circular son 



exposed, i.e. without covers. 



2. .4^osors=porsal-fruited Ferns, with the roundish sori 



becoming laterally confluent beneath the reflexed, 

 unaltered margins of the frond. 

 GYMNOGRAMMEj^jPb-ws whose linear 

 cases have no special corer. 



3. Gymnogramma=DoTsa,\-frmi,ed. Ferns, having the sori 



linear, forked, naked. 



AsPipiEM=J?erns whose sori have special indiisia, of a 

 circular or roundish foi*m, and springing here and 

 there, from the back of the veins. 



4. PoZysfo'c/iwm=Dorsal-fruited Ferns, having circular peltate 



indusia, attached by their centre. 



5. _asraz=Dorsal-fruited Ferns, having reniforin indusia, 



attached by their indented side. 



AspLENiEJE= J Ferns whose sori have special indusia, of an 

 oblong or elongated form, and springing from the sides 

 of the veins. 



C. ^Ay?'mm=Dorsal-fruited Ferns, having oblong reniform 



BS 



