Atratiformis: Answers to key questions in Sedges (Carex) of Saskatchewan, Fascicle 3, Flora of Saskatchewan by Anna Leighton leading to this species. The answers are in the order you would normally work through the key. 

	Stigmas 3; achenes three-sided, occasionally terete, though their shape may be concealed by flattened perigynia.  NOT [stigmas 2; achenes lenticular]
	Spikes 2 or more per culm, terminal and lateral; spike bracts present on lateral spikes (except in Section Phyllostachyae), lowest bract usually evident, often conspicuous.  NOT [Spikes 1 per culm, terminal; spike bracts absent].
	Lower pistillate scales not bract-like or leaf-like but similar in size and shape to individual perigynia (up to twice as long as perigynia in C. magellanica ssp. irrigua).  NOT [Lower pistillate scales resembling green, leaf-like bracts much longer and wider than individual perigynia]
	Perigynia glabrous. NOT [Perigynia sparsely to densely pubescent or puberulent (in C. pedunculata pubescence represented by very short hairs scattered near tip; in some species of Sect. Acrocystis, perigynia may be glabrous or virtually hairless, but all members of this group have convexly 3-sided to terete achenes with tight fitting perigynia and a stipe-like base about equal to beak in length)]
	Beak absent or less than 0.5 mm long; if more than 0.5 mm long, then terminating in an orifice without teeth. NOT [Beak over 0.5 mm long and usually visibly bidentate (teeth hyaline in C. sprengelii, inconspicuous in C. viridula, very short in C. oligosperma).]
	Leaves and sheaths glabrous; plants cespitose or rhizomatous. NOT [Leaves and sheaths pubescent; plants cespitose]
	Lowest spike bracts sheathless or with sheaths 1-2 mm long (to 3 or 4 mm long in Section Limosae).  NOT [Lowest spike bract sheath at least (2.5) 3 mm long]
	Plants cespitose or rhizomatous, usually taller than 2 dm (to 8 dm); terminal spike if staminate then wider than 2 mm or longer than 1 cm, or pistillate spikes long-stalked; leaves 1-6 mm wide; plants of boreal forest and grassland habitats. NOT [Plants densely tufted and low, usually less than 2 dm tall; terminal spike staminate (occasionally with a few pistillate flowers at base in C. glacialis), 1-2 mm wide and seldom over 1 cm long; pistillate spikes sessile or slightly stalked; leaves 0.4-1.5 mm wide; plants of rocky and/or sandy habitats in far north.]
	Lateral spikes on filiform stalks 0.5 cm long or longer, often nodding.  NOT [Lateral spikes sessile or erect on short stalks.]
	Terminal spike gynecandrous, not distinctly different in appearance from lateral pistillate spikes except for a V-shaped base consisting of staminate flowers; beak 0.4-0.5 mm long, bidenticulate; roots lacking felt-like covering of yellowish pubescence.  NOT [Terminal spike almost always staminate (occasionally gynecandrous in C. magellanica ssp. irrigua), distinctly narrower than lateral pistillate spikes; beak absent or less than 0.5 mm long, merely a hole or short tube or cone with no teeth; roots with a felt-like covering of yellowish pubescence.]