Key to the Species of Equisetum. 



Series I. — Evergreen species. Stems rough, seldom branched, 

 catkins usually tipped with a hard 

 point 

 Stems tall, stout, about as thick as a lead pencil 

 Sheaths dilated upward 



Margins incurved, stems rough 



E. Funstoni 

 Margins not incurved, stems smooth 

 E. lavigatiun 

 Sheaths not dilated upward 



Old stems much branched E. robustum 

 Old stems seldom branched 



Joints short. . E. hiemale 



Joints longer . E. Ferrissi 



Stems slender, tufted 



Six-angled, thread-like E. scirpoides 



More than six-angled, larger E. ■ua7-iegatitm 

 Series II. — Deciduous species, Rootstock only, perennial. 

 Stems smooth, usually branching, catkin 



not tipped with a hard point 

 Fertile stems tawny or flesh-coloured when young 

 Not lasting through the summer" 



Plants stout. Western . E. Telmaieia 

 Plants slender, mostly Eastern E. ar7iense 

 Lasting through the summer 



Branches of sterile stems unbranched 



E. pratense 

 Branches of sterile stems again branched 

 E, silvatlcum 

 Fertile stems green like the sterile 



Sheaths appressed . E. fluviatile 



Sheaths looser 



Spores perfect, abundant E. pahcstre 

 Spores imperfect, few E. li/torale 



