Schizachne purpurascens
 
Purple Oat-Grass

Palea

Moose Mountain Provincial Park
14-June-2021

Note the inner face is toward the flower.

The following items are taken from keys in Flora of Saskatchewan, Fascicle 4, Grasses of Saskatchewan by Anna L. Leighton and Vernon L. Harms.  Family Poaceae is first divided into tribes, then the tribes are divided into genera, and the genera divided into species.  However, there are a number of tribes that are very difficult to distinguish morphologically.  These are grouped into a large, artificial tribe I call "Multitribe".  Multitribe is then divided into groups, and each group is then divided into genera.  The answers are in the order you would normally work through the keys.

Multitribe: Answers to key questions leading to this tribe. 
Mature inflorescence, if breaking into units, then the units not as below; NOT [Mature inflorescence breaking into spikelet units consisting of a sessile fertile spikelet, a hairy pedicel with or without a sterile spikelet at tip, and a hairy rachis joint, all arising at the same point (a node) in specialized panicle branches called rames]
Spikelets not as below; sterile florets if present, either located distal to the fertile floret(s) on the rachilla or paired and attached at the base of a single fertile floret, not paired with the upper glume as below; lemma and palea variously textured, enclosing the flower or not; disarticulation usually above the glumes; NOT [Spikelets usually dorsally compressed, appearing 1-flowered but containing 1 fertile floret and 1 sterile floret, the latter attached to the base of fertile floret opposite the upper glume, resembling the upper glume, and together with the upper glume enveloping the fertile floret; lower glumes minute (sometimes absent) to 3/4 as long as upper glumes and typically wrapping most of the way around the pedicel at base; fertile floret seed-like with chartaceous-indurate lemma and palea enclosing flower and fruit; disarticulation below the glumes with rare exceptions]
Spikelets 1 to many-flowered, subtended by a pair of glumes (only 1 on lateral spikelets in Lolium); palea margins enclosed or not; plants of dry or wet habitats; NOT [Spikelets 1-flowered, lacking glumes; margins of the palea tightly enclosed by the lemma margins on female or perfect florets; plants of wetlands, often emergent aquatic]
Inflorescence not as below; if a terminal spike, then the lateral spikelets attached edgewise to the rachis with inner (upper) glume wanting (as in Lolium); NOT [Inflorescence a terminal spike with sessile or subsessile spikelets attached broadside at nodes on opposite sides of the rachis]
Lemmas and lemma awns not as below; if lemma indurate and enveloping the floret, then glumes distinctly dorsally compressed and calluses glabrous (as in Milium); NOT [Lemmas stiff to indurate, firmer than the glumes, surrounding the palea and often overlapping along the margins, closed at the tip as well as at the base, often pubescent; lemma awns (caducous or wanting in some species) terete and encircled at the base by the closed tip of the lemma; calluses usually pubescent, rarely glabrous]

Group3: Answers to key questions leading to this group. 
If plants mat-forming, then inflorescences not as below; NOT [Mat-forming annuals or perennials either with clusters of spikelets hidden by sharp-pointed leaves at branch tips, or with pistillate inflorescences consisting of burs partially hidden within expanded leaf sheaths with only the staminate inflorescences exceeding the upper leaves]
Inflorescence not as below, the spikelets usually on pedicels in panicles that range from spike-like to open; if spikelets sessile, then they either have more than 1 fertile floret per spikelet or are not arranged like the teeth of a comb; NOT [Inflorescence consisting of spike-like panicle branches with sessile- subsessile, closely imbricate, regularly-spaced, parallel spikelets all directed toward 1 side of the branch like the teeth of a comb (loosely so in Bouteloua curtipendula); fertile florets 1 per spikelet]
Spikelets with more than 1 fertile floret; sterile florets if present, attached above the fertile florets (Phragmites, with sterile florets attached above and below fertile florets, is an exception); NOT [Spikelets with 1 fertile floret; sterile florets if present, attached above or below the fertile floret]

Schizachne: Answers to key questions leading to this genus. 
Inflorescence a panicle with all spikelets subtended by 2 glumes; NOT [Inflorescence a terminal spike; lateral spikelets positioned edgewise to the rachis and lacking a glume on inside edge]
Spikelets usually pedicellate; if sessile-subsessile, then not arranged as below; NOT [Spikelets sessile or subsessile on spike-like panicle branches, or on short secondary branches in dense one-sided clusters at branch tips]
Rachillas glabrous or pubescent; if pubescent, then hairs much shorter than the lemmas; panicles and plants not as below; NOT [Rachillas with silky hairs (4) 6-10 mm long, as long as the lemmas or nearly so; panicles 15-35 (45) cm long, 8-20 cm wide at maturity, dense, feathery; plants 10-30 (40) dm tall, with stout, creeping rhizomes and often forming dense stands]
Glumes < 17 mm long; if glumes longer, then plants perennial; NOT [Glumes 18-32 mm long, usually exceeding the lemmas; plants annual]
Plants without the below combination of characteristics; NOT [Culm sheaths closed to near summit; leaf blades flat; spikelets 12-40 (55) mm long; lemmas 7-14 (21) mm long, usually awned, the awns terminal or subterminal; calluses glabrous; ovaries and caryopses with pubescent apical appendage; caryopses adnate to paleas at maturity]
Plants without the below combination of characteristics; NOT [Rachilla conspicuously pubescent with straight hairs; calluses bearded; spikelet 2 (3-4) flowered; lemma 2-4 toothed, sometimes obscurely so, sometimes entire; lemma awns attached dorsally or just below apex, often exceeding the lemma apex by only 1-2 mm (awn may be absent in Trisetum wolfii)]
Lemmas awned, the awns 3-17 mm long, slightly outcurving or geniculate, attached dorsally about midlength, or at base of 0.5-8 mm long apical teeth; calluses with dense or long hairs; NOT [Lemmas unawned or awned; if awns present, then the awns straight and terminal or subterminal, and the calluses glabrous or with short, sparse hairs]
Lemma nerves evident, usually raised; lemmas glabrous; ligules membranous; lemma awns not obviously flattened or flattened proximally; NOT [Lemma nerves obscure; lemmas glabrous or pubescent on the back with margins usually pubescent; ligules a fringe of hairs; lemma awns flattened their whole length]
Lemma awns attached dorsally just below apical teeth, slightly outcurving or geniculate; rachillas glabrous; ligules 0.5-1.5 mm long; glumes distinctly shorter than the adjacent lemmas; leaf sheaths closed to top but splitting open from the top down; NOT [Lemma awns attached dorsally at about midlength well below the bifid apex, geniculate; rachillas pubescent; ligules 2-3 (4) mm long; glumes about the same length as the adjacent lemmas; leaf sheaths open]