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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) |
3 Leaves all 2- even-pinnate, the basalmost " pinna pair" usually replaced by a pair of leaflets larger than the others, the pinnae and the leaflets often 'straying' to subopposite or fully alternate arrangement (some pinnae appearing odd-pinnate); leaflets 3-6 cm long, acuminate at the apex; trunks 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. |
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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. |
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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. |
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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. |
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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 |