Fluviatilis: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan by V. L. Harms, A. L. Leighton, and M. A. Vetter leading to this species. The answers are in the order you would normally work through the key. 

Inflorescences branched panicles with 4 - 12 branches; styles trifid; achenes 3.8 - 5.5 mm long, markedly trigonous or achenes only slightly compressed, retaining bristles when shed; beaks to 0.8 mm long; achene epidermal cells small and about as deep as wide in cross-section, resulting in achenes that sink in water; summit of sheath ventral strip papery with veins reaching apex or near to apex; plants of freshwater aquatic habitats and wetlands.  NOT [Inflorescences usually unbranched, sometimes with 1-4 branches; styles bifid, only rarely trifid; achenes 2.3 - 4.1 mm long, usually biconvex, rarely compressed-trigonous, not retaining bristles when shed (or only 1 - few bristles sometimes weakly persistent); beaks minute, less than 0.5 mm long; achene epidermal cells enlarged in cross-section, 2 - 3+ times deeper than wide, resulting in achenes that float in water; summit of sheath ventral strip usually a veinless, membranous, triangle; plants of brackish to saline or alkaline aquatic habitats and wetlands.]

Bolboschoenus: Answers to key questions in Rushes, Bulrushes & Pondweeds plus the remaining Monocots of Saskatchewan by V. L. Harms, A. L. Leighton, and M. A. Vetter leading to this genus. 

	Flowers and achenes naked in the axils of scales, not enclosed in a sac; flowers usually perfect (sometimes some flowers imperfect in Cyperus, Rhynchospora and Cladium).  NOT [Flowers and achenes enclosed in a sac (perigynium) borne in the axils of scales; flowers imperfect.]
	Perianth bristles absent or up to 6 per flower; if more than 6, then only somewhat longer than the achenes.  NOT [Perianth bristles usually more than 10 per flower, much longer than the achenes, conspicuously elongated to over 10 mm long in fruit stage and usually obscuring most scales in spikelets.]
	Inflorescence not a solitary, terminal spike; if solitary, terminal and spike-like, then inflorescence +/- terete.  NOT [Inflorescence a compressed, solitary, terminal spike bearing few-flowered spikelets attached in 2 rows.]
	Inflorescence usually with > 1 spikelet; if only 1 spikelet present, then inflorescence bract usually 10-200 mm long (but as short as 7 mm in Schoenoplectus subterminalis) and achenes 2 -3.5 mm long.  NOT [Inflorescence a solitary terminal spikelet; inflorescence bracts absent or up to 8 mm long and only slightly longer than the spikelet; achenes usually <= 2 mm long (up to 2.3 mm in Eleocharis quinqueflora)]
	Achenes lacking a tubercle but sometimes beaked.  NOT [Achenes with a narrowly triangular tubercle.]
	Scales of spikelets spirally arranged; spikelets terete.  NOT [Scales of spikelets 2-ranked; spikelets flattened or 4-sided.]
	Plants without the following combination of characteristics.  NOT [Culms tall and slender, 30 - 100 cm high and 1 - 2 mm wide; inflorescences with stiffly ascending primary and secondary branches supporting 100 - 1,000 spikelets in compact clusters; achenes terete with bases discoid, truncate, impressed and flared.]
	Inflorescences subtended by 2 or more leaf-like, erect to spreading bracts; longest bracts exceeding the inflorescence; leaves basal and cauline, or all cauline with cauline leaf blades well developed.  NOT [Inflorescences not subtended by leaf-like bracts, the proximal bract terete, trigonous or thickly C-shaped in cross-section and resembling a continuation of the culm (making the inflorescence appear to be attached to the side of the culm although the bract may be pushed aside in Amphiscirpus as the spikelets mature); longest bracts exceeding the inflorescence or not; usually all leaves basal with blades often much shorter than their sheaths.]
	Spikelets fewer (ours < 40 per inflorescence) and large (7 - 40 mm long (ours), (4) 6 - 10 mm wide); anthers 2 - 4+ mm long; scales puberulent to glabrescent with awns 1 - 3 mm long; achenes 2.3 - 5.5 mm long; culms cormose at base.  NOT [Spikelets numerous (50 - 500 per inflorescence) and small (2 - 8 mm long (ours), 1- 3.5 mm wide); anthers ca. 1 mm long (ours); scales glabrous, apiculate, mucronate or with awns to 0.6 (1.2) mm long (ours); achenes 0.6 - 1.8 mm long; culms not cormose at base.]

Cyperaceae: Answers to key questions in Budd's Flora leading to this family. 

	plants not aquatic, or if growing in water, most of the plant emersed; NOT [plants aquatic, floating or submerged, with floating leaves or emersed inflorescence]
	culms usually solid; NOT culms usually hollow]
	leaves three-ranked; NOT [leaves two-ranked]
	inflorescence NOT [a dense, single, cylindrical spike 8-15 cm long, 1-2.5 cm thick], if a single spike, less than 1 cm thick
	flowers not in globular heads; NOT [flowers in globular heads, the upper ones staminate, the lower ones pistillate]
	flowers solitary in the axil of a single bract (scale); NOT [flowers enclosed in two-ranked bracts with the lowest (glumes) empty]
	perianth inconspicuous, not in two whorls; NOT [perianth present, conspicuous, in two series of 3 segments, often brightly colored]
	perianth reduced to bristles; NOT [perianth reduced to minute lodicules or lacking]