8. Fruit an inflated capsule, 30-50 mm long; inflorescence a terminal thyrse; corolla yellow…Koelreuteria
8. Fruit a globose drupe, tan at maturity, 10-15 mm in diameter; inflorescence an axillary panicle; corolla lavender…Melia
3. Leaves 1-pinnately compound…9.
9. Leaves even-pinnately compound (generally with 2 leaflets at the apex of the rachis, these obviously and symmetrically paired)…Gleditsia
9. Leaves odd-pinnately compound (generally with a single leaflet at the terminus of the rachis)…10.
10. Stems armed with prickles or stipular or nodal spines; leaves often also with prickles…11.
11. Leaves not aromatic when fresh, lacking pellucid punctate glands; leaves never with prickles on the rachis; leaflet apices rounded…Robinia
11. Leaves strongly aromatic when fresh, with conspicuous pellucid punctate glands; leaves often with prickles on the rachis; leaflet apices usually acuminate…Zanthoxylum
10. Stems unarmed (leaflets with spinose margins in some species, or the stem with dense hispid hairs)…12.
12. Leaflets entire…13.
13. Plant a medium or tall tree…14.
14. Leaflets alternate on the rachis...15.
15. Leaflets obovate (or elliptic), broadest above or in the middle; flowers perfect, bilaterally symmetric, papillionaceous, white; fruit a legume...Cladrastis
15. Leaflets lanceolate, broadest below the middle; perianth of male flowers reduced to two linear-lanceolate tepals, perianth of female flowers with 5 tepals, yellow green to red; fruit a drupe...Pistacia
14. Leaflets opposite on the rachis, leaflets (1-) 2-5 (-6) cm long…16.
16. Flowers in an upright, stiff raceme or panicle; flowers creamy white with some blue; stamens connate at the very base…Maackia
16. Flowers in dangling racemes; flowers white or pink; stamens diadelphous or connate at the very base…Robinia
13. Plant a shrub or small tree to 7 (-10) m tall…17.
17. Flowers bilaterally symmetrical, papilionaceous; stamens 10; fruit a legume; leaves with stipules…Robinia
17. Flowers radially symmetrical, stamens 3-5; fruit a drupe; leaves without stipules…18.
18. Rachis winged between each pair of leaflets; inflorescences dense...Rhus
18. Rachis not winged or only between terminal one or two pairs of leaflets; inflorescences openly branched...19.
19. Fruits red; leaflets lanceolate; foliage and stems lacking contact poisons; urban forests and wood lots...Pistacia
19. Fruits white or yellow; leaflets ovate, elliptic, or oblong; foliage and stems containing contact poisons; bogs, streamhead pocosins, seeps...Toxicodendron
12. Leaflets serrate or crenate…20.
20. Leaflets crenate, the teeth rounded and often inconspicuous…21.
21. Leaflets (especially the basal and on the basalscopic side) with 1-5 large rounded teeth, each bearing a prominent dark green gland; leaf rachis not winged; fruit a schizocarp, with 2-5 samaroid mericarps; plant a medium to large tree…Ailanthus
21. Leaflets with obscure crenations, not as below nor bearing glands; leaf rachis narrowly to conspicuously winged, especially towards the tip; fruit a drupe; plant a shrub or small tree…Rhus
20. Leaflets serrate…22.
22. Inflorescences axillary…23.
23. Fruit with husk dehiscent into 4 valves; pith of twigs continuous; leaves with (3-) 5-17 (-19) leaflets, the largest usually the terminal or final 2 lateral; nut with shell smooth, ridged, or irregularly wrinkled (but not deeply furrowed); terminal buds with imbricate (overlapping) or valvate scales…Carya
23. Fruit with husk indehiscent; pith of twigs chambered (not always developing until autumn of the first year's growth); leaves with (7-) 11-19 (-23) leaflets, the largest usually about halfway up the leaf; nut with shell deeply furrowed in a complex corrugated pattern; terminal buds with valvate…Juglans
22. Inflorescences terminal…24.
24. Inflorescence corymbose (flat-topped or rounded, as wide as long or wider); fruit a red pome…Sorbus
24. Inflorescence paniculate (longer than wide); fruit various (see below), but not as above...25.
25. Fruit an inflated membranaceous capsule…Koelreuteria
