24 BRITISH PERNS. 



Var. microdon. Pinnae only lobed or subpinnate at 



the base, wavy. 



9. A. Adiantum-nigrum. Frond bipinnate, triangular; 

 segments wedge-oblong. 



Var. acutum. Fronds tripinnate, triangular, much 

 acuminate ; segments linear, acute. 

 Genus 8. CETERACH, WiUdenow. 

 1. G. officinarum. The only British species. 



Genus 9. SCOLOPENDRIUM, Smith. 



1. S. vulgare. The only British species. Fronds strap- 

 shaped, entire. 



Var. polyschldes. Fronds long, narrow, irregularly 



lobed, fertile. 

 Var. marginatum. Fronds long, narrow, lobed, with a 



double, i.e. split margin, fertile. 

 Var. crispum. Fronds elongated, much undulated at 

 the margin, usually barren. 



Genus 10. BLECHNTJM, Linnaeus. 

 1. B. Spicant. The only British species. 

 Genus 11. PTERIS, Linnaeus. 

 1. P. aquilina The only British species. 



Genus 12. ADIANTUM, Linnceus. 

 1. A. Capillus-Veneris. The only British species. 

 Genus 13. CYSTOPTERIS, Bernhardi. 



1. C.fragili*. Fronds lanceolate, bipinnate, pinnules ovate, 



acute, toothed or lobed sori central. 



Var. dentata. Pinnules ovate, obtuse, bluntly toothed, 



distinct ; sori marginal. 



Var. Dickieana. Pinnules broad, obtuse, slightly 

 , blunt-toothed, overlapping ; sori marginal 



2. G. regia. Fronds lanceolate, subtripinnate, segments 



linear. 



3. G. montanct. Fronds triangular, tripinnate. 



Genus 14. WOODSIA, R. Brown. 



1. W.Uvensis. Fronds lanceolate, hair-scaly; pinnse oblong, 



deeply lobed. 



2. W. alpina. Fronds linear, almost smooth ; pinnae bluntly 



triangular, lobed. 



Genus 15. TRiCHOMANES, Linnceus. 

 1. T. radicals, The only British species. 



