rhachis

Spikelets 2–many-flowered, panicled; the flowers herbaceo-chartaceous, or becoming harder, of firmer texture than the large and mostly unequal empty glumes; the uppermost flower imperfect; rhachis and base of the flower often bearded.

From The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee by Asa Gray

Spikelets spicate, in pairs, the pedicellate sterile or rudimentary; rhachis bearded.

From The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee by Asa Gray

Spikes solitary, racemed or spiked; the rhachis somewhat extended beyond the spikelets.

From The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee by Asa Gray

A tree 20–60° high; leaflets 4–9 pairs, obliquely lanceolate, sharply acuminate, entire, 1½–3´ long; the rhachis of the leaf not winged; flowers white, in a large panicle, fruit mostly globose, 6´´ broad.

From The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee by Asa Gray

Spikelets 1–4-flowered, subterete, usually in dense heads; scales oppressed, several-nerved, the lower empty and often persistent after the fall of the rest of the spikelet; joints of the rhachis winged, enclosing the triangular achene.

From The Manual of the Botany of the Northern United States Including the District East of the Mississippi and North of North Carolina and Tennessee by Asa Gray