Hordeum jubatum
 
Foxtail Barley

Rachis Node Side A, Close-Up

Moose Mountain Provincial Park
23-June-2021

There are three spikelets per node - a fertile, sessile, central spikelet (parts labeled in turquoise) and two sterile, pedicellate, lateral spikelets (parts labeled in red and yellow).  Each spikelet has two long, narrow glumes (labeled G) and a single floret containing a lemma terminated with a short (lateral spikelets) or long (central spikelet) awn (labeled LA).  The palea of the floret from the central spikelet is labeled P.

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.

Triticeae: 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 a terminal spike with sessile or subsessile spikelets attached broadside at nodes on opposite sides of the rachis; NOT [Inflorescence not as above; if a terminal spike, then the lateral spikelets attached edgewise to the rachis with inner (upper) glume wanting (as in Lolium)]

Hordeum: Answers to key questions leading to this genus. 
Spikelets 2 or more per node, occasionally 1 at some nodes; NOT  [Spikelets 1 per node, occasionally 2 at some nodes]
Spikelets 3 per node with 1 floret per spikelet; florets in central spikelet always fertile, those in the 2 lateral spikelets sterile and greatly reduced in plants that disarticulate at rachis nodes but may be fertile in plants with a continuous rachis; NOT [Spikelets 2-7 per node with 1-7 (9) florets per spikelet; if spikelets 3 per node, then some spikelets with more than 1 floret]

Jubatum: Answers to key questions leading to this species. 
Lateral spikelets pedicellate and sterile; auricles absent; spikes disarticulating at rachis nodes at maturity; NOT [Usually one or both lateral spikelets sessile and fertile; auricles to 6 mm long, well-developed; spikes usually not disarticulating at maturity]
Glumes 15-85 mm long, moderately to strongly divergent; awns of lemma in central spikelet 11-90 mm long; NOT [Glumes 7-19 mm long, ascending to slightly divergent; awns of lemma in central spikelet 3.5-14 mm long]