1	Annuals; culms usually branched		(2)
+	Perennials; culms usually unbranched		(4)
2 (1)	Lemma 1.7–2 mm; central awn 0.5–0.8 cm.		1 A. cumingiana
+	Lemma 5–11 mm; central awn 1–2.5 cm		(3)
3 (2)	Glumes subequal or lower glume slightly shorter; lemma distinctly longer than upper glume.		2 A. adscensionis
+	Glumes unequal, lower glume 1/2–2/3 length of upper glume; lemma ± equal to upper glume.		3 A. depressa
4 (1)	Lower glume longer than upper glume; panicle open, branches divaricate, bearded in axils.		4 A. chinensis
+	Lower glume shorter than upper glume or glumes subequal; panicle narrow, branches erect or ascending, glabrous in axils		(5)
5 (4)	Column of awn 1–3 mm, twisted; lateral awns 5–10 mm		(6)
+	Column of awn absent or very short and straight; lateral awns reduced, 0.1–3 mm, or up to 6 mm		(7)
6 (5)	Leaf sheaths and blades glabrous; glumes and lemma smooth (rarely scabrid); anthers 3.5–4 mm.		5 A. tsangpoensis
+	Leaf sheaths and blades with silky hairs; glumes and lemma scabrid or lemma with long soft hairs; anthers 4–4.5 mm.		6 A. scabrescens
7 (5)	Lateral awns 0.1–0.4 mm.		7 A. brevissima
+	Lateral awns 1.1–6 mm		(8)
8 (7)	Glumes 7–10 mm, lemma 6.5–8 mm, central awn 4–8 mm		(9)
+	Glumes 12–13 mm; lemma ca. 9 mm, central awn 8–9 mm.		10 A. alpina
9 (8)	Lateral awns 1.1–3 mm; apex of glumes acute, upper mucronate; leaf sheaths smooth.		8 A. triseta
+	Lateral awns 5–6 mm; apex of glumes obtuse or emarginate; leaf sheaths scaberulous.		9 A. batangensis