1 Leaves 2-foliolate or 1-foliolate (and then deeply notched).

..2 Leaves 1-foliolate (2-lobed)

..2 Leaves 2-foliolate

1 Leaves 3-, 5-, to many-foliolate.

....3 Leaves 3-foliolate.

......4 Plant a liana, climbing by twining, by tendrils, or by adventitious roots.

........5 Leaves untoothed and unlobed

........5 Leaves coarsely toothed or lobed. {add Eleutherococcus trifoliatus ARALIACEAE}

..........6 Leaflets obovate or broadly elliptic (broadest at or above the middle), the teeth or lobes primarily or solely in the apical half of the leaf; plant climbing by leaf-opposed tendrils

..........6 Leaflets orbicular or ovate (broadest at the middle or below the middle), the teeth or lobes primarily or solely in the basal half of the leaf; plant climbing by stem twining or by dense, reddish adventitious roots.

............ 7 Plant climbing by the stem twining; [plant not actually woody, but so robust as to often be assumed to be so]

............ 7 Plant climbing by dense, reddish adventitious roots attaching the stem to tree trunks or rock outcrops

......4 Plant a shrub (sometimes scrambling or occasionally high-climbing with the support of other vegetation, but lacking the specialized climbing structures listed above).

............ ..8 Stems armed with small prickles or stout thorns.

............ ....9 Stems with stout thorns at the nodes; fruit a hesperidium (orange-like, but densely hairy)

............ ....9 Stems with many small prickles along the internodes; fruit either a legume, or an aggregate of drupelets, or a hip.

............ ......10 Leaflets with 2 rounded lateral lobes near the base, otherwise entire; fruit a legume

............ ......10 Leaflets serrate and sometimes also cleft; fruit either an aggregate of drupelets or a hip

............ ..8 Stems unarmed.

............ ........11 Leaflets serrulate, crenulate, serrate, with a few coarse and jagged teeth (spine-tipped or not), or shallowly lobed.

............ ..........12 Leaflets serrulate or crenulate

............ ..........12 Leaflets serrate, with a few coarse and jagged teeth (spine-tipped or not), or shallowly lobed.

............ ............ 13 Leaflets with 2 prominent, rounded lobes near the base; fruit a legume; flowers > 3 cm long, corollas bilaterally symmetrical, red, in a terminal raceme

............ ............ 13 Leaflets serrate and sometimes also cleft, or with a few coarse and jagged teeth (spine-tipped or not); fruit either a tan or red drupe or a red berry; flowers < 1 cm across, corollas radially symmetrical, green, yellow, or white, in axillary or terminal panicles or racemes

............ ............ ..14 Leaflets with a few spine-tipped teeth; fruit a red berry; [TX westwards]

............ ............ ..14 Leaflets not spine-tipped; fruit a red or tan drupe; [collectively widespread]

............ ........11 Leaflets entire and unlobed.

............ ............ ....15 Terminal leaflet sessile.

............ ............ ......16 Leaflets < 2 cm long; stems and branches dark green

............ ............ ......16 Leaflets 5-15 cm long; stems and branches tan to brown

............ ............ ....15 Terminal leaflet with a petiolule.

............ ............ ........17 Leaves pinnately trifoliolate, a rachis present as an extension of the petiole past the point of attachment of the 2 lateral leaflets, the terminal leaflet borne on a petiolule at the terminus of the rachis, with an obvious joint present between the rachis and petiolule

............ ............ ........17 Leaves palmately trifoliolate, the terminal leaflet typically with a longer petiolule than the lateral leaflets, but lacking a rachis (the petiolule of the terminal leaflet attached at the same point as the 2 lateral leaflets and unjointed)

....3 Leaves with 5-many leaflets (poorly developed leaves in some species with only 3 leaflets).

............ ............ ..........18 Leaves palmately or palmately-pedately compound.

............ ............ ............ 19 Leaves palmately-pedately 5-foliolate (the lateral 2 leaflets on each side borne on a common Y-shaped stalk).

............ ............ ............ ..20 Leaflets entire; sap milky

............ ............ ............ ..20 Leaflets toothed; sap clear

............ ............ ............ 19 Leaves palmately compound (all the leaflets attached at a single point).

............ ............ ............ ....21 Leaves > 6 dm wide

............ ............ ............ ....21 Leaves < 3 dm wide.

............ ............ ............ ......22 Leaflets with entire margins

............ ............ ............ ......22 Leaflets with serrate margins.

............ ............ ............ ........23 Stems armed with prickles scattered in the internodes

............ ............ ............ ........23 Stems unarmed or with paired nodal spines.

............ ............ ............ ..........24 Inflorescence an umbel; leaves evergreen, glossy; stems often with paired nodal spines

............ ............ ............ ..........24 Inflorescence a panicle; leaves deciduous, dull; stems unarmed

............ ............ ..........18 Leaves pinnately, bipinnately, or complexly compound.

............ ............ ............ ............ 25 Leaves at least in part pinnate-pinnatifid, 2-pinnate, or otherwise more complexly compound than 1-pinnate.

............ ............ ............ ............ ..26 Leaves evenly 2-pinnately compound

............ ............ ............ ............ ..26 Leaves oddly pinnate-pinnatifid, 2-pinnately compound, or more complexly compound than 2-pinnate.

............ ............ ............ ............ ....27 Leaves pinnate-pinnatifid, with 7-19 leaflets, each leaflet pinnatifid into narrowly lanceolate lobes; {upper leaflet surface dark green, lower surface silvery with gray sericeous pubescence}

............ ............ ............ ............ ....27 Leaves 2-pinnately compound, or even more complexly compound.

............ ............ ............ ............ ......28 Plant a liana, climbing by tendrils

............ ............ ............ ............ ......28 Plant a shrub or tree, not climbing.

............ ............ ............ ............ ........29 Plant armed with prickles on the stem, and sometimes also on the axes and main veins of the leaves

............ ............ ............ ............ ........29 Plant unarmed.

............ ............ ............ ............ ..........30 Plant a shrub, < 2.5 m tall.

............ ............ ............ ............ ............ 31 Foliage green; leaflets ovate, acute at the tip; flowers 3-merous, the tepals white or cream; fruit a red berry

............ ............ ............ ............ ............ 31 Foliage blue-green; leaflets obovate, rounded or notched at the tip; flowers 4-5-merous, the sepals green, the petals yellow; fruit a capsule

............ ............ ............ ............ ..........30 Plant a tree, > 3 m tall when flowering and fruiting.

............ ............ ............ ............ ............ ..32 Leaflets serrate.

............ ............ ............ ............ ............ ....33 Fruit a globose drupe, tan at maturity, 10-15 mm in diameter; inflorescence an axillary panicle; corolla lavender

............ ............ ............ ............ ............ ....33 Fruit an inflated capsule, 30-50 mm long; inflorescence a terminal thyrse; corolla yellow

............ ............ ............ ............ 25 Leaves 1-pinnately compound.

............ ............ ............ ............ ............ ......34 Leaves even-pinnately compound (generally with 2 leaflets at the apex of the rachis, these obviously and symmetrically paired).

............ ............ ............ ............ ............ ........35 Leaflets rounded to obtuse at the apex (or acute to acuminate in Gymnocladus); fruit a legume; inflorescence various, but not as below

............ ............ ............ ............ ............ ........35 Leaflets acuminate at the apex; fruit a drupe or capsule; inflorescence a panicle with many, small, radially symmetrical flowers.

............ ............ ............ ............ ............ ..........36 Fruit a capsule.

............ ............ ............ ............ ............ ..........36 Fruit a drupe.

............ ............ ............ ............ ............ ............ 37 Tree dioecious; drupe ca. 5 mm long; stamens (of male flowers) 3-5 (-7)

............ ............ ............ ............ ............ ............ 37 Tree bisexual; drupe ca. 13 mm long; stamens 8-10

............ ............ ............ ............ ............ ......34 Leaves odd-pinnately compound (generally with a single leaflet at the terminus of the rachis).

............ ............ ............ ............ ............ ............ ..38 Leaves very large, > 10 dm long

............ ............ ............ ............ ............ ............ ..38 Leaves small to large, < 10 dm long.

............ ............ ............ ............ ............ ............ ....39 Stems armed with prickles or stipular or nodal spines; leaves often also with prickles.

............ ............ ............ ............ ............ ............ ......40 Leaves with conspicuous leafy stipules, often adnate to the petiole; plant a liana or small to medium shrub; leaves serrate, often sharply and prominently so; leaves not strongly aromatic when fresh, lacking pellucid punctate glands on the surface

............ ............ ............ ............ ............ ............ ......40 Leaves lacking leafy stipules; plant a tree or tall shrub; leaves entire or obscurely crenate or serrate; plant a tree or tall shrub; leaves either strongly aromatic when fresh, with conspicuous pellucid punctate glands or not aromatic and not pellucid-punctate.

............ ............ ............ ............ ............ ............ ........41 Leaves not aromatic when fresh, lacking pellucid punctate glands; leaves never with prickles on the rachis; leaflet apices rounded

............ ............ ............ ............ ............ ............ ........41 Leaves strongly aromatic when fresh, with conspicuous pellucid punctate glands; leaves often with prickles on the rachis; leaflet apices usually acuminate

............ ............ ............ ............ ............ ............ ....39 Stems unarmed (leaflets with spinose margins in some species, or the stem with dense hispid hairs).

............ ............ ............ ............ ............ ............ ..........42 Leaflets entire.

............ ............ ............ ............ ............ ............ ............ 43 Plant a liana, climbing by twining

............ ............ ............ ............ ............ ............ ............ 43 Plant an upright shrub or tree, not climbing.

............ ............ ............ ............ ............ ............ ............ ..44 Plant a medium or tall tree.

............ ............ ............ ............ ............ ............ ............ ....45 Leaves with stipules; flowers bilaterally symmetrical, papilionaceous, white, cream, or pink; stamens 10; fruit a legume; [collectively widespread in our area]

............ ............ ............ ............ ............ ............ ............ ....45 Leaves without stipules; flowers radially symmetrical, whitish; stamens 5 or 10; fruit a single-seeded drupe; [FL peninsula]

............ ............ ............ ............ ............ ............ ............ ..44 Plant a shrub or small tree to 7 (-10) m tall.

............ ............ ............ ............ ............ ............ ............ ......46 Leaf 2-5 cm long, with 5-7 leaflets

............ ............ ............ ............ ............ ............ ............ ......46 Leaf > 8 cm long, with 5-many leaflets.

............ ............ ............ ............ ............ ............ ............ ........47 Flowers bilaterally symmetrical, papilionaceous (reduced in Amorpha to a single petal); stamens 10; fruit a legume; leaves with stipules.

............ ............ ............ ............ ............ ............ ............ ........47 Flowers radially symmetrical, stamens 4-5; fruit either a drupe (Anacardiaceae), or a 1-3-seeded berry or a samara (Picramniaceae); leaves without stipules.

............ ............ ............ ............ ............ ............ ............ ..........48 Inflorescence a panicle; fruit a drupe; [collectively widespread]

............ ............ ............ ............ ............ ............ ............ ..........48 Inflorescence a raceme or compound thyrse; fruit a samara or 1-3-seeded berry; [s. FL]

............ ............ ............ ............ ............ ............ ..........42 Leaflets serrate or crenate.

............ ............ ............ ............ ............ ............ ............ ............ 49 Leaflets crenate, the teeth rounded and often inconspicuous.

............ ............ ............ ............ ............ ............ ............ ............ ..50 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

............ ............ ............ ............ ............ ............ ............ ............ ..50 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

............ ............ ............ ............ ............ ............ ............ ............ 49 Leaflets serrate.

............ ............ ............ ............ ............ ............ ............ ............ ....51 Leaf serrations spinose

............ ............ ............ ............ ............ ............ ............ ............ ....51 Leaf serrations not spinose.

............ ............ ............ ............ ............ ............ ............ ............ ......52 Inflorescences axillary.

............ ............ ............ ............ ............ ............ ............ ............ ........53 Plant a tree, freely branched; rhizome inner bark not brightly colored; flowers unisexual, the male flowers in catkins, the female flowers solitary or few in a spike, the perianth greenish or tan and inconspicuous; fruit a nut covered by a dehiscent or indehiscent involucre

............ ............ ............ ............ ............ ............ ............ ............ ........53 Plant a short shrub, < 1 m tall, little branched; rhizome inner bark of fresh plants bright yellow; flowers bisexual, petals absent, the 5 petaloid sepals maroon; inflorescence a drooping panicle from the base of the new year’s growth; fruit an aggregate of follicles

............ ............ ............ ............ ............ ............ ............ ............ ......52 Inflorescences terminal.

............ ............ ............ ............ ............ ............ ............ ............ ..........54 Inflorescence corymbose (flat-topped or rounded, as wide as long or wider); fruit a red pome

............ ............ ............ ............ ............ ............ ............ ............ ..........54 Inflorescence paniculate (longer than wide); fruit various (see below), but not as above.

............ ............ ............ ............ ............ ............ ............ ............ ............ 55 Leaves stipulate; flowers bright white; fruit an aggregate of 5 follicles

............ ............ ............ ............ ............ ............ ............ ............ ............ 55 Leaves lacking stipules; flowers cream or yellow; fruit either a drupe or an inflated membranaceous capsule.

............ ............ ............ ............ ............ ............ ............ ............ ............ ..56 Fruit a drupe

............ ............ ............ ............ ............ ............ ............ ............ ............ ..56 Fruit an inflated membranaceous capsule

1 Leaves variously modified from strict 2-even-pinnateness, either with 1) a mixture (on a tree) of 1-even-pinnate and 2-even-pinnate leaves, and/or 2) the pinnae or leaflets often subopposite or fully alternate, and/or 3) with an odd number of pinnae per leaf (the tip of the rachis with a pair of lateral pinnae and a terminal pinna, but the leaflets of the pinnae still in opposite pairs), and/or 4) the basal pair of pinnae evolutionarily replaced by a single pair of leaflets larger than the other leaflets.

..2 Flowers small, inconspicuous, in catkin like-racemes or racemes of racemes; perianth greenish-white or greenish-yellow, with a cylindrical hypanthium to 10 mm long and shorter perianth lobes; flowers mostly unisexual; large trees; fruits woody and indehiscent at maturity, 1-5 cm wide[ collectively widespread in our region, but absent from s. FL and s. TX].

....3 Leaves characteristically a mixture (on a tree) of 1-even-pinnate (mainly on spurs) and 2-even-pinnate (mainly on new growth), the pinnae and the leaflets strictly opposite or subopposite; leaflets 1.5-4 cm long, acute to rounded at the apex; trunks with simple, trident, or multiply branched thorns to 20 cm long (or unarmed)

..2 Flowers either with conspicuous petals or aggregated into spikes or spherical heads with showy stamens; petals either (Caesalpinoids) yellow, orange, red, or (Mimosoids) the tubular perianth whorls less conspicuous than the stamens, these yellow to orange; flowers bisexual; small shrubs, shrubs, small or medium trees, or large trees (if large trees, then of tropical parts of our region); fruits papery or chartaceous (rarely woody), often < 2 cm wide; [collectively widespread, including of s. FL and s. TX].

......4 Leaves with pinnae and leaflets mostly subopposite or fully alternate; [exotic, s. FL]; [Mimosoid]

......4 Leaves with an odd number of pinnae per leaf (the tip of the rachis with a pair of lateral pinnae and a terminal pinna), but the leaflets in opposite pairs; [native or exotic, TX and OK]; [Caesalpinoid].

........5 Shrub or small tree, 5-50 dm tall; sepals ovate; leaflets not glandular, or with glands only along the leaflet margin

........5 Sprawling shrub, less than 6 dm tall; sepals linear; leaflets glandular punctate across the lower surface (these orange in life, drying black)

1 Leaves strictly 2-even-pinnate (with pinna pairs borne opposite one another and no pinna terminal on the rachis, and with leaflets also born in opposite pairs).

..........6 Pinna pairs 1-6 (-7) per leaf; leaflets 4-ca. 250 per leaf.

............ 7 Leaflets 1.5-14 mm long.

............ ..8 Glands absent on petioles and rachises.

............ ....9 Dwarf shrub, 1-6 dm tall; branches unarmed.

............ ....9 Shrub, small tree, or scrambling liana; branches armed with straight nodal spines or internodal catclaw prickles.

............ ......10 Branches armed with paired, straight, nodal spines, these simple or 3-branched; branches and larger stems green, photosynthetic; flowers caesalpinoid, 2-2.5 cm in diameter.

............ ......10 Branches armed with catclaw prickles scattered along internodes; branches and stems brown; flowers caesalpinoid or mimosoid.

............ ........11 Scrambling liana; flowers caesalpinoid, 1.5-2 cm across

............ ........11 Shrub; flowers mimosoid, aggregated into spherical inflorescences 9-15 mm in diameter

............ ..8 Glands (stalked, columnar, or domed) 1 or more on petioles or rachises, on the petiole or at rachis nodes.

............ ..........12 Branches unarmed.

............ ............ 13 Stamens connate basally into a tube; spherical inflorescences whitish or cream, 15-23 mm in diameter

............ ............ 13 Stamens free; spherical inflorescences yellow, 6-8 mm in diameter

............ ..........12 Branches armed with straight nodal spines or internodal catclaw prickles.

............ ............ ..14 Branches armed with catclaw prickles scattered along internodes.

............ ............ ..14 Branches armed with paired, straight, nodal spines.

............ ............ ....15 Leaflet pairs 2-6 per pinna; inflorescences cylindrical.

............ ............ ......16 Petiolar/rachis glands at nodes of the rachis, short-columnar; stamens connate basally into a tube

............ ............ ......16 Petiolar/rachis gland on the petiole; stamens free

............ ............ ....15 Leaflet pairs 6-25 per pinna; inflorescences spherical (or cylindrical in Prosopis laevigata).

............ ............ ........17 Inflorescences cylindrical; leaflet pairs 15-27 per pinna

............ ............ ........17 Inflorescences spherical; leaflet pairs 6-20 per pinna.

............ ............ ..........18 Dwarf shrub; pinna pair 1 per leaf; leaflet pairs 6-11 per pinna; fruit spirally twisted into a cylinder

............ ............ ..........18 Shrub or small tree; pinna pairs 2-5 (-6) per leaf; leaflet pairs 9-20 per pinna; fruit flat, straight.

............ ............ ............ 19 Spherical inflorescences 15-23 mm in diameter; stamens connate basally into a tube; fruits flat, about 1 cm wide, 2-4 mm thick

............ ............ ............ 19 Spherical inflorescences 6-13 mm in diameter; stamens free; fruits turgid, cylindrical, about 1 cm in diameter (wide and thick)

............ 7 Leaflets 10-60 mm long (at least the larger leaflets on a plant > 14 mm long).

............ ............ ............ ..20 Glands absent on petioles and rachises.

............ ............ ............ ....21 Pinna pairs 1 per leaf; branches unarmed; flowers red-pink, mimosoid, aggregated into spherical inflorescences 5-7 cm in diameter

............ ............ ............ ....21 Pinna pairs 2-5 per leaf; branches armed with catclaw prickles scattered along internodes; flowers yellow to orange, caesalpinoid, each flower 0.7-2 cm across.

............ ............ ............ ......22 Liana climbing and sprawling over other vegetation; flowers 0.7-1 cm across

............ ............ ............ ......22 Shrub or small tree; flowers 1.8-2 cm across

............ ............ ............ ..20 Glands (stalked, columnar, or domed) 1 or more on petioles or rachises, on the petiole or at rachis nodes.

............ ............ ............ ........23 Leaflet pair 1 per pinna

............ ............ ............ ........23 Leaflet pairs 3-14 per pinna

............ ............ ............ ..........24 Branches usually armed with paired, straight, nodal spines; inflorescences cylindrical; stamens 10

............ ............ ............ ..........24 Branches unarmed; inflorescences spherical; stamens many.

............ ............ ............ ............ 25 Stamens free

............ ............ ............ ............ 25 Stamens connate basally into a tube.

............ ............ ............ ............ ..26 Petiolar gland near base of petiole; spherical inflorescences either 0.9-1.7 cm in diameter, or 5-6 cm in diameter

............ ............ ............ ............ ..26 Petiolar gland closer to first pinna pair than to petiole base; spherical inflorescences 2-2.6 cm in diameter

..........6 Pinna pairs 4-25 per leaf (at least the larger leaves on a plant with > 6 pinna pairs); leaflets 150-3000 per leaf.

............ ............ ............ ............ ....27 Leaflets 10-40 mm long, at least the larger on a leaf > 15 mm long.

............ ............ ............ ............ ......28 Leaf rachis eglandular; flowers caesalpinoid, each yellow-orange and 3-4 cm across

............ ............ ............ ............ ......28 Leaf rachis with cupular glands at nodes; flowers mimosoid, pink, aggregated into a spherical head 5-6 cm in diameter

............ ............ ............ ............ ....27 Leaflets 1-15 mm long.

............ ............ ............ ............ ........29 Glands absent on petioles and rachises.

............ ............ ............ ............ ..........30 Branches armed with catclaw prickles scattered along internodes; shrub; flowers mimosoid, white, cream, or pink, aggregated into spherical heads 0.9-2 cm in diameter.

............ ............ ............ ............ ..........30 Branches unarmed; tree; flowers caesalpinoid, each yellow and 2-3.5 cm across

............ ............ ............ ............ ........29 Glands (stalked, columnar, or domed) or nonglandular spheroid projections 1 or more on petioles or rachises, on the petiole or at rachis nodes.

............ ............ ............ ............ ............ 31 Branches unarmed.

............ ............ ............ ............ ............ ..32 Fruits 30-60 cm long, woody, persistent and indehiscent on the tree; flowers caesalpinoid, scarlet and yellow, 8-10 cm across; rachis with spheroidal projections at the nodes; petiole lacking glands

............ ............ ............ ............ ............ ..32 Fruits < 20 cm long, papery, coriaceous, or woody; flowers mimosoid, white, cream, pink, or pale yellow, aggregated into spherical heads 1-6 cm in diameter; rachis lacking spheroidal projections; petiole bearing domed or saucer-shaped glands along the petiole or at the 1st pair of pinnae.

............ ............ ............ ............ ............ ....33 Spherical heads pink, 2.5-6 cm in diameter

............ ............ ............ ............ ............ ....33 Spherical heads white, cream, or pale yellow, 0.5-2.2 cm in diameter.

............ ............ ............ ............ ............ ......34 Fruits strongly coiled; stamens many; tree

............ ............ ............ ............ ............ ......34 Fruits strait or slightly curved; stamens 10; tree or shrub.

............ ............ ............ ............ ............ ........35 Stipules persistent and evident, 3-10 mm long; fruits 5.5-8.5 cm long, 2-5 mm wide

............ ............ ............ ............ ............ ........35 Stipules caducous; fruits 8-20 cm long, 10-20 mm wide

............ ............ ............ ............ ............ 31 Branches variously armed, with nodal spines, thorn spurs, or catclaw prickles scattered along internodes.

............ ............ ............ ............ ............ ..........36 Branches armed with catclaw prickles scattered along the internodes

............ ............ ............ ............ ............ ..........36 Branches armed either with woody thorn spurs or paired nodal spines.

............ ............ ............ ............ ............ ............ 37 Branches armed with stout thorn spurs (these simple or branched); inflorescences cylindrical, bicolored, the base of pink or whitish staminodes, the tip of yellow stamens; fruits flattened, but also curved and contorted

............ ............ ............ ............ ............ ............ 37 Branches armed with paired nodal spines, these either narrow and needle-like or massive, hollow, and with an entrance hole; fruits turgid, straight or slightly curved