Bolboschoenus

Z. Hroudová, P. Zákravský, M. Ducháček & K. Marhold, Taxonomy, distribution and ecology of Bolboschoenus in Europe in Ann. Bot. Fennici 44. 2007
but key modified
1Inflorescence consisting of sessile spikelets and (4-)5-6(-8) rays; achenes 2.2-2.5 x 1.4-1.7 mm, in cross-section exocarp thinner than mesocarp
1'Inflorescence consisting of sessile spikelets only or sessile spikelets and 1-2(-4) rays; achenes 3-4 x (1.8-)2.1-2.7 m, in cross-section exocarp thicker than mesocarp