466 Key to the System of 



1978. Stems triangular 1979 



Stems cylindrical or somewhat compressed ... ... 1981 



1979. Leaves nearly trigonous. 



Shoots creeping ; stem firm ; leaves two or few, elongated, 

 rigid, channelled and keeled-angular ; spikelets few or 

 several in a lateral cluster, all sessile ; floral bracts usually 

 dark -brown, pointed from below the bilobed summit ; 

 rudimentary sepals and petals reduced to bristlets or 

 partly absent; apex of the anthers pointed, rough; 

 stigmas two or three ; fruit bi- or tri- angular, broadest 

 upwards. S. pungens. 



Leaves nearly flat ... ... ... ... ... 1980 



1980. Spikelets quite large, but hardly numerous, yellowish- 



or dark-brown. 



Stems leafy, often partly submerged ; leaves very long, 

 broad -linear, keeled, but otherwise flat ; spikelets gene- 

 rally in a leafy somewhat compound terminal cyme ; 

 summit of the floral bracts receding from the terminal 

 point ; rudimentary sepals and petals reduced to bristlets 

 or partly absent ; fruit bi- or tri-angular, almost truncate 

 but pointed, shining. S. maritimus. 



Spikelets very numerous, but hardly large, blackish- 

 green. 



Stems leafy, very tall ; leaves broad-linear, at the margin 

 and keel rough, the floral leaves also much elongated ; 

 spikelets large, dispersed or oftener clustered in a com- 

 pound leafy cyme ; rudimentary sepals and petals changed 

 into much elongated capillary bristlets, variously curved 

 and towards the upper end densely ciliolated ; fruit pale ; 

 plan-convex, on the outer side bluntly angular, slightly 

 pointed. S. poly st achy us. 



1981. Stems robust, bearing a cyme of large spikelets. 



Often very tall and partly submerged ; stems of soft texture, 

 cylindrical or very slightly compressed ; basal leaves 

 often undeveloped, occasionally flattened, one conspicuous 

 almost cylindric and pointed floral leaf continuing the 

 stem ; spikelets large, many-flowered, in an almost ter- 

 minal generally compound cyme, either dispersed or 

 clustered ; floral bracts brown, broad, blunt or infra- 

 terminally pointed ; rudimentary sepals and petals reduced 

 to reversedly rough bristlets or partly absent ; stigmas 

 two or three ; fruit bi- or tri-angular. S. lacustris. 



