1 Leaves minutely honeycombed-reticulate beneath (best seen at magnification of 40-100×), more-or-less strongly whitened (and otherwise variously glabrous or pubescent); [Fraxinus americana complex].

  2 Samara wings arising near base of the body; [trees of swamps of GA and FL]

  2 Samara wings arising near summit of body; [trees of mesic to xeric upland sites, collectively widespread in our area].

    3 Leaflet blades mostly 3-6 (-8) cm long, suborbicular-ovate to obovate, oblong-ovate, or elliptic, the apex abruptly acute to rounded, base rounded; rachis (1-) 2-6 (-7) cm long; leaf scars 2.5-3 (-4) mm wide; [sc. OK south to sc. TX]

    3 Leaflet blades mostly 5.5-12 (-15) cm, ovate to ovate-lanceolate or elliptic-lanceolate, the apex acute-acuminate or less commonly obtuse, base cuneate to rounded; rachis 4-12 cm long; leaf scars 3-4 mm wide; [collectively widespread in our region].

      4 Petiole bases and leaf scars V- to U- or crescent-shaped with a deeply concave or notched upper margin; samaras (19-) 25-32 (-38) mm long, samara wings 3-5 (-6) mm wide, samara bodies (5-) 6-11 mm long, 1.5-2.5 mm wide; twigs, petioles, petiolules, and rachises glabrous

      4 Petiole bases and leaf scars oblong-obovate to widely obovate with a nearly truncate or very shallowly bowl-shaped upper margin; samaras (32-) 33-54 mm long, samara wings (4.5-) 5-8 mm wide, samara bodies (7-) 10-15 mm long, 2-4 mm wide; twigs, petioles, petiolules, and rachises glabrous or hirtellous to hirtellous-puberulent to tomentulose.

        5 Twigs, petioles, petiolules, and rachises sparsely to densely hirtellous to hirtellous-puberulent or tomentulose; samaras 33-54 mm long, samara wings 6-8 mm wide, samara bodies (7-) 11-15 mm long, 2-4 mm wide

1 Leaves not minutely-honeycombed-reticulate beneath (sometimes with papillae and small scales visible at 40×, but these not forming a developed netlike pattern), pale green (and otherwise variously glabrous or pubescent).

          6 Youngest twigs 4-angled to narrowly 4-winged; petiole bases raised on a distinct pedestal; lateral leaflets sessile to subsessile; [of dry to mesic sites].

             7 Samara bodies strongly flattened and often nearly indistinct from wings, wings 5-8 mm wide; buds black to blackish brown; leaf scars shallowly hemispheric, apex truncate; flowers bisexual and unisexual

             7 Samara bodies flattened but clearly distinct from wings, wings 8-10 mm wide; buds gray to reddish brown; leaf scars crescent-shaped, apex concave; flowers bisexual

          6 Youngest twigs terete; petiole bases flush with stem; lateral leaflets sessile to subsessile or petiolulate; [of mesic to wetland sites].

               8 Lateral leaflets sessile; samara bodies strongly flattened and often nearly indistinct from wings; buds black to blackish brown, corky-ridged

               8 Lateral leaflets petiolulate; samara bodies distinct from wings; buds brownish, not corky-ridged.

                 9 Samara wings arising abruptly from the upper (distal) 1/5-1/4 (-1/2) of the samara body; samara wings 4-7 mm wide

                   10 Leaflets 3-5, coriaceous to subcoriaceous, (4-) 5-9.5 × (1.5-) 2-4 cm, the margins coarsely and sharply serrate on distal 1/2--2/3; leaf scars shallowly hemispheric, the apex shallowly concave; samaras mostly 2-winged but often with some 3-winged among the 2-winged ones, the wings gradually expanded from near base to distal 1/3 of the body and narrowly flanging the body; [TX & OK]

                   10 Leaflets 5-7 (-9), subcoriaceous to submembraneous, (6-) 7.5-11 (-12) × 2.5-5 (-6) cm, the margins subentire to inconspicuously dentate-serrulate; leaf scars broadly oblong-ovate, the apex truncate to very shallowly concave; samaras consistently 2-winged, the wings arising abruptly from distal 1/4-1/5 (-1/2) of the body; widespread

                 9 Samara wings arising from the base or lower (proximal) 1/4 of the samara body; samara wings (5.5- ) 6-20 (-22) mm wide.

                     11 Trees, 15--30(--40) m tall; leaflet blades (7-) 9-15 (-25) cm long × (2.5-) 3.5-7 (-11) cm wide, the bases often rounded, sometimes obtuse to acute or acuminate; samaras (35-) 40-70 (-75) mm long, the wings gradually expanded from near the base of the body to the proximal 1/2, (5.5-) 6-10 (-12) mm wide

                     11 Shrubs, trees, or shrublike trees, 2.5-12 (-15) m tall; leaflet blades 4-12 (-15) cm long × (1-) 2-5 (-6) cm wide, the bases acute to truncate or rounded; samaras (25-) 30-50 (-54) mm long, the wings arising either from the base of the body to the proximal 1/4 or from the middle/proximal 3/4 of the body, 6-20 (-22) mm wide.

                       12 Samaras 35-46 mm long × (10-) 12-20 (-22) mm wide, rhombic to broadly elliptic, elliptic-obovate, oblong-obovate, or rhombic-ovate; wings 2 (-3), lateral veins (11-) 13-19 on each wing (side)

                       12 Samaras (25-) 30-50 (-54) long × 7-10 (-12) mm wide, obovate-oblanceolate to narrowly obovate or narrowly elliptic-obovate; wings 2 (very rarely 3), lateral veins 5-9 on each wing (side)