Riggins’ 1969 Key

KEY TO SPECIES 1. Florets glabrous

2. Lemma 1-nerved, white or tinged with purple; glumes shorter than floret; spikelets (1.3) 1.6 — 2.8 mm long; lower blades 3.0 — 12.0 cm long; lower sheaths 0.5 — 1.5 (2.0) mm wide when folded; caryopsis falling from the floret and pericarp becoming gelatinous when moist

… ⇒ S. neglectus

2. Lemma 3- nerved, pale yellow and. irregularly mottled with dark areas; glumes longer than the floret; spikelets (glabrous ) 2.3 — 3.8 (4.2) mm long; lower blades (5.5) 8.0 — 26.0 cm long; lower sheaths (1.0) 1.5 — 3.0 mm wide when folded

… ⇒ S. ozarkanus

l. Florets pubescent

3. Lower sheaths (1.0) 1.5 — 3.0 mm wide when folded; lower blades (5.5) 8.0 — 26.0 cm long; spikelets (pubescent) 1.9 — 2.0 (5.4) mm long; glumes longer than the floret; lemmas 3-nerved; floret length/width ratio 1.6 — 3.3 (3.8)

… ⇒ S. ozarkanus

3. Lower sheaths 0.8 — 1.7 mm wide when folded; lower blades 4.5 — 11.0 cm long; spikelets 2.0 — 4.9 (6.0) mm long, glumes usually shorter than the floret; lemmas 1- and 3-nerved; floret length/width ratio 2.2 — 5.7 (7.5)

… ⇒ S. vaginiflorus