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1 Primary branches with 0-1 compressed basal internodes (in the basalmost 1 cm or so); culm internodes usually sulcate (with a groove extending upward from the node, sometimes partly obscured by the branch); culm leaves deciduous; culms to 10 m tall; rhizomes lacking air canals; foliage leaf blades 0.8-1.3 cm wide
1 Primary branches with 2-5 compressed basal internodes (in the basalmost 1 cm or so); culm internodes usually terete; culm leaves persistent to tardily deciduous; culms to 4 m tall; rhizomes with or without longitudinal air canals (visible in cross-section as a cylinder of hollow canals 1 mm or less from the outer surface); foliage leaf blades 0.8-2 cm wide.
..2 Foliage blades coriaceous, persistent; lower leaf surfaces densely pubescent or glabrous, strongly tessellate; primary branches usually > 50 cm long
....3 Primary branch basal nodes not developing secondary branches; primary branches usually < 35 cm long; foliage blade abaxial surfaces sparsely pilose or glabrous; auricles absent; top knot blades 9-22.5 cm long; [AL north to e. TN and w. NC]
....3 Primary branch basal nodes developing secondary branches; primary branches 12-49 cm long; foliage blade abaxial surfaces long pubescent; auricles present; top knot blades 9-37 cm long; [known from AL]