Fabaceae subfam. Caesalpinioideae
(synonym of Fabaceae subfam. caesalpinioideae)
Acacia
acacia, wattle
erect to ascending or pendulous, glabrous or pubescent;
twigs not flexuous or slightly so, terete to angled or ridged, short shoots usually absent.
bipinnate, sometimes pinnate or tripinnate, 2-foliolate, or phyllodic.
alternate (except fascicled or whorled in A. verticillata), even-bipinnate or phyllodic, leaves often modified (in age) to polymorphic phyllodes (enlarged, flattened petiole without leaflets), usually glandular on margins and/or apex, saplings often with even-pinnate juvenile leaves often not present at maturity;
stipules usually present, usually early deciduous, rarely woody, spinose;
petiolate, usually with 1 globose gland;
pinnae [1 or] 2–31[–50] pairs, mostly opposite;
leaflets 8–70 pairs per pinna, opposite, sessile or subsessile, blade margins entire, surfaces glabrous or pubescent.
20–200+-flowered, terminal or axillary, globose heads or cylindrical spikes, heads solitary, fascicled, or clustered, or arranged in pseudoracemes or pseudopanicles;
bracts present.
usually not elongated in fruit, glabrous or pubescent.
caesalpinioid (noncaesalpinioid in Ceratonia) or mimosoid, bilateral or radial;
sepals distinct or connate;
petals (0 or)5(or 6), distinct or connate;
stamens (2–)5–250+, filaments distinct or connate, heteromorphic or some or all sometimes modified or staminodial, anthers basifixed or dorsifixed;
pollen in monads, tetrads, or polyads.
mimosoid;
calyx cup-shaped, lobes 4 or 5, triangular, glabrous [pubescent];
corolla yellow to cream, cup-shaped, lobes 4 or 5, triangular, membranous, glabrous [pubescent];
stamens 20–150, rarely connate basally, usually exserted, mostly yellow to gold or creamy white;
anthers dorsifixed, mostly eglandular;
ovary sessile or short-stipitate;
style and stigma filiform.
legumes, dehiscent or indehiscent, or loments (in Prosopis).
legumes, erect to pendulous, stipitate, stipe usually relatively short, mostly flat, straight to falcate, linear to oblong, apex sometimes beaked, usually dehiscent along sutures, dry, papery to leathery, glabrous or pubescent.
usually with an apical hilum, complex hilar valve absent, pleurogram on each face, open or closed;
embryo straight.
usually 6–10, usually flattened, ellipsoid to ovoid, uniseriate, usually with pulpy, bright-colored aril, forming a cap or encircling seed.
nectaries often present on petiole or rachis, sometimes stipular or bracteal.
lateral, free, or absent.
= 7, 8, 9, 11, 12, 13, 26, 28.
= 13.
Fabaceae subfam. Caesalpinioideae
Acacia
Genera 148, species ca. 4400 (38 genera, 174 species in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species ca. 1300 (15 in the flora).
Acacia species are indigenous mostly in the Southern Hemisphere, with more than 950 in Australia. None is native to the New World.
To preserve as much current usage as possible, at the 17th International Botanical Congress in 2005, the type of the genus Acacia was changed from Acacia scorpioides (Linnaeus) W. Wright to the Australian species Acacia penninervis Sieber ex de Candolle (B. R. Maslin 2008; J. McNeill and N. J. Turland 2010). Presently, there is considerable evidence that the broadly defined genus Acacia is not a natural or monophyletic group (Gill. K. Brown et al. 2008). Therefore, plants of the former Acacia subg. Phyllodineae remain in the genus Acacia (Maslin et al. 2003; Maslin 2008), and other species of the traditional Acacia are transferred to the genera Acaciella, Mariosousa, Parasenegalia Seigler & Ebinger, Pseudosenegalia Seigler & Ebinger, Senegalia, and Vachellia.
Members of Acacia enumerated here are introduced, exotic species proven to be adventive in the United States by vouchered collections; most are restricted to Arizona, southern California, and Florida. In addition, many Australian Acacia species are cultivated in botanical gardens and plant introduction centers and as ornamentals in the nursery trade. Although not clearly established to be adventive, other Acacia species may occasionally be found outside of cultivation; D. Isely (1973) mentioned a few of these, including A. podalyriifolia A. Cunningham ex G. Don, reported from a non-cultivated stand on Santa Catalina Island, California, and more recently from Orange County. Naturalized individuals of A. salicina Lindley and A. stenophylla A. Cunningham ex Bentham are known from Maricopa County, Arizona (ASU). Acacia iteaphylla F. Mueller ex Bentham is naturalized on the University of California-Riverside campus and is possibly invasive (Sanders & Morgan 21588, UCR).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key to Genera of Subfamily Caesalpinioideae, Excluding Mimosoid Clade
2. Corollas absent; inflorescences often on older branches and trunk; leaves even-pinnate; legumes flat with thickened margins. | Ceratonia |
2. Corollas present; inflorescences not usually on older stems or trunk; leaves even- or odd-pinnate, often bipinnate; legumes flat or cylindric, without thickened margins. | → 3 |
3. Trees, often armed (with straight or branching thorns); inflorescences spicate clusters; flowers polygamous or dioecious; corollas not obvious; leaves clustered from spurs. | Gleditsia |
3. Trees, shrubs, or herbs, armed or unarmed; inflorescences not spicate clusters; flowers bisexual; corollas obvious; leaves clustered on spurs or not clustered. | → 4 |
4. Stamen filaments proximally villous, much longer than anthers; stems photosynthetic, yellowish green; leaves clustered, alternate from spurs, bipinnate but sometimes appearing pinnate; legumes constricted between seeds. | Parkinsonia |
4. Stamen filaments glabrous, usually nearly same length as anthers; stems not photosynthetic, brownish (except Senna armata); leaves not clustered on spurs, pinnate. | → 5 |
5. Trees; leaf petiole and rachis without glands; stamens 10, filaments of 3 abaxial stamens sigmoidally incurved, usually longer than anthers; legumes indehiscent, not corrugated over seeds; inflorescences usually terminal. | Cassia |
5. Herbs, shrubs, or trees; leaf petiole and rachis with or without glands; stamens (2 or)3–10, all filaments straight; legumes dehiscent or indehiscent, often corrugated over seeds; inflorescences terminal or axillary. | → 6 |
6. Bracteoles absent; petals subequal; stamens 6–10, usually dwindling from one side to the other; legumes either indehiscent or tardily dehiscent through 1 or both sutures, if the latter then not coiling, or valves breaking into 1-seeded joints; stipules inconspicuous; flowers in axillary racemes, sometimes aggregated into compound racemes; root nodules absent. | Senna |
6. Bracteoles present; petals unequal; stamens (2 or)3–10, radially symmetric or bilateral, equal or irregularly unequal; legumes elastically dehiscent, valves coiling; stipules conspicuous, striate, often persistent; flowers in reduced few-flowered axillary racemes; root nodules present. | Chamaecrista |
1. Leaves bipinnate (sometimes also pinnate, rarely unifoliolate). | → 7 |
7. Trees; flowers usually unisexual, appearing apetalous, polygamous or dioecious; petals and sepals small and similar, greenish yellow; legumes usually pulpy between seeds. | → 8 |
8. Trees unarmed; leaves bipinnate, leaflet blade margins entire; inflorescences terminal, racemes or panicles; legumes thick, turgid, woody; seeds 2–5, subglobose. | Gymnocladus |
8. Trees often armed with simple or branched thorns (cultivars sometimes unarmed); leaves bipinnate in terminal growth, pinnate from spur shoots, leaflet blade margins often crenulate; inflorescences axillary, spicate racemes; legumes usually thin, flat, flexible; seeds 1–25(–30), compressed to subterete. | Gleditsia |
7. Trees, shrubs, herbs, or vines; flowers bisexual, obviously petalous; petals and sepals easily differentiated; legumes not pulpy between seeds. | → 9 |
9. Trees, 8–35 m, unarmed. | → 10 |
10. Corollas yellow, less than 25 mm diam., petals not clawed; calyx imbricate; stigma peltate, broad; stipules 1 mm, triangular, entire; legumes 4–12 cm, margins winged, indehiscent; seeds 1–4. | Peltophorum |
10. Corollas scarlet and yellow, 80–100 mm diam., petals clawed; calyx valvate; stigma capitate; stipules 5–15 mm, pinnate; legumes 30–60 cm, margins not winged, dehiscent; seeds 20–40. | Delonix |
9. Herbs, shrubs, subshrubs, or small trees to 6 m, armed or unarmed. | → 11 |
11. Leaves odd-bipinnate. | → 12 |
12. Leaflet blades not glandular-punctate (inflorescences often conspicuously glandular-pubescent); calyx persistent in fruit. | Hoffmannseggia |
12. Leaflet blades glandular-punctate; calyx deciduous or persistent in fruit. | → 13 |
13. Shrubs, trees, or perennial herbs; stipules ovate, lanceolate-ovate to deltate or suborbiculate, usually early deciduous, persistent, or subpersistent; sepals ovate-lanceolate to orbiculate, persistent in fruit; androecium and gynoecium free, not cupped in lower sepal; legumes lanceolate-oblong; leaflet blades eglandular or with conspicuous black, sessile glands along margin, these sometimes sunken in sinuses of crenulated margin. | Erythrostemon |
13. Shrubs, subshrubs, or perennial herbs; stipules filiform or linear to lanceolate, persistent or tardily deciduous; sepals linear, deciduous in fruit; androecium and gynoecium cupped in the lower sepal; legumes oblong, oblong-lanceoloid, lunate, or ovate; leaflet blades with multiple orange, glandular dots on abaxial surfaces (drying black). | Pomaria |
11. Leaves even-bipinnate. | → 14 |
14. Legumes covered with prickles on faces; seeds ovoid or globose to subglobose, 15–25 mm wide; flowers functionally unisexual, segregated on separate male and female racemes. | Guilandina |
14. Legumes not covered with prickles; seeds ovoid or ellipsoid, 4–10 mm wide; flowers bisexual. | → 15 |
15. Legumes indehiscent, compressed or subterete, valves not twisting. | → 16 |
16. Branches brown or gray-brown; legumes oblong, compressed, ± fleshy, leathery; calyx irregular, abaxialmost sepal covering others in bud; petals yellow, banner with red medial markings. | Tara |
16. Branches green or yellowish green; legumes oblong to linear, compressed or subterete, sometimes torulose; calyx nearly radially symmetric, valvate, sepal lobes nearly distinct; petals all yellow, banner without red markings. | Parkinsonia |
15. Legumes dehiscent, valves twisting, laterally-compressed. | → 17 |
17. Corollas yellow to orange or red; petals glabrous. | Caesalpinia |
17. Corollas consistently yellow, banner sometimes with red marks; petals pubescent. | Denisophytum |
Key to Genera of Subfamily Caesalpinioideae, Mimosoid Clade
1. Stamens 5–10. | → 2 |
2. Shrubs or trees, usually armed with nodal spines or thorns; fruits legumes or loments, indehiscent or dehiscent, elongate, turgid, and often irregularly moniliform, or coiled springlike, rarely irregularly twisted or contorted. | → 3 |
3. Pinnae 1 or 2 pairs; fruits loments, straight or spirally coiled, seeds distinct nearly to base; inflorescences axillary, spikes or globose heads, 40–100+-flowered, corollas yellow, cream-yellow, purple-brown, greenish white, or yellow-green, all bisexual; sc, sw United States. | Prosopis |
3. Pinnae 7–15 pairs; fruits legumes, contorted or coiling at maturity; inflorescences axillary, pendent spikes, 50–200-flowered, corollas pale green, distally bisexual with bright yellow anthers, and proximally sterile with purple or white staminodes; introduced, Florida. | Dichrostachys |
2. Herbs, shrubs, or trees, unarmed, or with internodal prickles which are generally curved and flattened; fruits legumes, dehiscent or segmenting. | → 4 |
4. Perennial herbs, unarmed, terrestrial or floating-aquatic; stems ascending, decumbent, prostrate, prostrate-ascending, or floating; corollas yellow-green to white; distal flowers often bisexual, proximal flowers sterile with petaloid staminodes (monomorphic in N. lutea). | Neptunia |
4. Trees, shrubs, subshrubs, or perennial herbs, usually unarmed, sometimes armed, terrestrial; stems erect, ascending, decumbent, prostrate, or sprawling; corollas white, cream, yellow, greenish white, pink, purple, or purple-pink; flowers usually bisexual. | → 5 |
5. Trees, 5–15(–40) m, unarmed; leaflet blades 15–45 mm, alternate; inflorescences in terminal panicles or axillary spikelike racemes; corollas white to cream; legumes straight to falcate or contorted, swollen around seeds, valves twisting; seeds glossy red, flattened; stipitate anther glands present; introduced, Florida. | Adenanthera |
5. Trees, shrubs, subshrubs, or herbs, 0.1–3 m, unarmed or armed; leaflet blades 1.5–26(–30) mm, opposite; inflorescences in heads, spikes, or racemes; corollas white, greenish white, pale green, yellow, or pink to purple; legumes straight or curved, not swollen around seeds; seeds not glossy red; stipitate anther glands absent. | → 6 |
6. Petiole nectar glands absent; legumes often craspedial, segmented into 1-seeded portions separating from persistent sutures (replum), sometimes unsegmented; plants armed with recurved or straight prickles or unarmed; corollas white or pink to purple. | Mimosa |
6. Petiole nectar gland present (sometimes minute); legumes not craspedial; plants without prickles; corollas white, greenish white, or yellow. | → 7 |
7. Shrubs or trees, 2–18(–20) m; stems erect; stipules ovate, inconspicuous; inflorescences globose heads; corollas yellow, white, or greenish white; legumes shortly stipitate, linear or oblong, compressed or flat, valves sometimes curling. | Leucaena |
7. Herbs or shrubs, to 3 m; stems erect to prostrate or decumbent; stipules subulate, small but evident; inflorescences condensed heads or spikes; corollas pale green or white; legumes sessile, linear or falcate, subterete to flattened, splitting along margins at maturity. | Desmanthus |
1. Stamens 14–250. | → 8 |
8. Filaments distinct (except rarely connate basally in Acacia); leaves bipinnate or simple phyllodia. | → 9 |
9. Leaves simple phyllodia or bipinnate; stipular spines usually absent (except A. paradoxa); seeds usually with pulpy aril forming a cap or encircling seed. | Acacia |
9. Leaves bipinnate; stipular spines present or absent; seeds usually without pulpy aril (except sometimes in Vachellia). | → 10 |
10. Stipular spines present, sometimes enlarged and inhabited by ants; ovaries sessile or subsessile; seeds sometimes surrounded by pulp. | Vachellia |
10. Stipular spines absent; ovaries stipitate; seeds not surrounded by pulp. | → 11 |
11. Petiolar glands absent; prickles absent; inflorescences usually in globose heads; corollas greenish white, drying to pink-rose; stamens 175–250, creamy white, anther glands absent. | Acaciella |
11. Petiolar glands usually present; prickles present or absent; inflorescences spikes or heads; corollas white to creamy white or yellow; stamens 35–160, white, small anther glands sometimes present. | → 12 |
12. Prickles usually present; stipules caducous; inflorescences terminal or axillary, heads or spikes, usually in pseudoracemes or pseudopanicles; ovaries stipitate or sessile, with nectariferous disc at base; stamens creamy or yellow, fading to reddish brown. | Senegalia |
12. Prickles absent; stipules persistent; inflorescences axillary, cylindrical spikes; ovaries short-stipitate, nectariferous disc absent; stamens white. | Mariosousa |
8. Filaments fused into a tube, monadelphous; leaves bipinnate. | → 13 |
13. Legumes usually dehiscent into 2 valves, sometimes craspedial; nectary glands present or absent. | → 14 |
14. Trees, shrubs, or herbs, unarmed; stipular spines absent. | → 15 |
15. Petiole nectary glands present; inflorescences axillary spikes or racemes; legumes straight, flat, membranous, with 2 prominent suture ribs surrounding periphery and detaching after dehiscence (craspedial); exocarp dark purple to blackish, exfoliating. | Lysiloma |
15. Petiole nectary glands absent; inflorescences axillary or terminal heads sometimes in short pseudopanicles; legumes straight or slightly curved, dehiscent longitudinally along sutures, valves strongly recurving; exocarp dark brown to green, not exfoliating. | → 16 |
16. Heads globose; corollas greenish white; stamens 30–60; legumes dehiscing elastically from distal end to proximal end. | Zapoteca |
16. Heads ± hemispheric or obconic; corollas reddish or whitish; stamens (14–)19–28; legumes dehiscing longitudinally along sutures but not elastically. | Calliandra |
14. Shrubs or trees, usually armed; stipular spines present. | → 17 |
17. Legumes recurved to coiled into a circle; seeds with aril; petiolar nectary gland between lowest pair of pinnae; leaflet blade venation pinnate. | Pithecellobium |
17. Legumes straight; seeds without an aril; petiolar nectary gland borne between distalmost pair(s) of pinnae; leaflet blade venation brochidodromous. | Havardia |
13. Legumes indehiscent, dehiscent, or late dehiscent; nectary glands present. | → 18 |
18. Legumes falcate or forming a nearly complete flattened spiral, valves woody, dull light brown to maroon or blackish; inflorescences racemes, pseudoracemes, or heads (fascicles) or flowers solitary. | → 19 |
19. Pinnae 2 or 3 pairs; inflorescences pseudoracemes from short shoots; legumes falcate, light brown to maroon. | Ebenopsis |
19. Pinnae 4–10(–15) pairs; inflorescences heads; legumes forming a nearly complete flattened spiral, blackish. | Enterolobium |
18. Legumes straight or slight curved, valves papery, membranous, leathery, or if woody, glossy red-brown; inflorescences umbels, spikes, racemes, or heads. | → 20 |
20. Legumes turgid, fleshy, pulpy, margins thickened, septate between seeds; flowers dimorphic, peripheral flowers smaller than central; introduced, Florida. | Samanea |
20. Legumes flat, not fleshy or pulpy, not septate between seeds; flowers sometimes dimorphic; Florida (Lysiloma), California (Paraserianthes), or widespread (Albizia). | → 21 |
21. Legumes with prominent sutural ribs surrounding periphery and persistent, not separating from the valves (or tardily), seeds released through decay of valves; Florida. | Lysiloma |
21. Legumes without prominent peripheral ribs, raised over seeds; widespread. | → 22 |
22. Pinnae 20–30+ pairs; inflorescences axillary, racemes, flowers homomorphic, corollas greenish; stamens ± 90, equaling petals, greenish to lemon yellow; legumes indehiscent or late-dehiscent; introduced, California. | Paraserianthes |
22. Pinnae (1 or)2–12 pairs; inflorescences axillary or terminal, heads or corymbs; flowers dimorphic, corollas whitish or pink to yellow-green; stamens 20–70, usually long-exserted, pink or white; legumes dehiscent or late-dehiscent; widespread. | Albizia |
1. Leaves compound. | → 2 |
2. Leaves with 2–5 pinna pairs; petioles 0–2 mm. | A. baileyana |
2. Leaves with (3–)6–31 pinna pairs; petioles 5–33 mm. | → 3 |
3. Distance between pinna pairs 7–20 mm; leaflet blades 5–15 mm. | A. decurrens |
3. Distance between pinna pairs 2–7 mm; leaflet blades 1.5–5 mm. | → 4 |
4. Rachis glands between most pinna pairs. | A. dealbata |
4. Rachis glands scattered, at pinna pair nodes and internodes. | A. mearnsii |
1. Leaves phyllodic. | → 5 |
5. Phyllodes 5–30 mm. | → 6 |
6. Stipular spines present. | A. paradoxa |
6. Stipular spines absent. | → 7 |
7. Phyllodes inequilateral, ± triangular, 5–15 mm wide, alternate. | A. cultriformis |
7. Phyllodes acicular, linear, 0.5–1.5 mm wide, fascicled or whorled. | A. verticillata |
5. Phyllodes (20–)30–250 mm. | → 8 |
8. Phyllodes with pinnate venation. | → 9 |
9. Pulvinus 4–8 mm; phyllodes 10–35 mm wide. | A. pycnantha |
9. Pulvinus 1–3.5 mm; phyllodes 3–14(–25) mm wide. | → 10 |
10. Globose heads 5–7 diam.; phyllode gland not obvious, not disciform. | A. retinodes |
10. Globose heads 8–12 mm diam.; phyllode gland obvious, disciform. | A. saligna |
8. Phyllodes with parallel venation. | → 11 |
11. Inflorescences cylindrical spikes. | → 12 |
12. Phyllodes falcate; flowers 5-merous. | A. auriculiformis |
12. Phyllodes not falcate; flowers 4-merous. | A. longifolia |
11. Inflorescences globose heads. | → 13 |
13. Twigs fragrant (vanilla-scented) when crushed, resin-ribbed. | A. redolens |
13. Twigs not fragrant when crushed, not resinous. | → 14 |
14. Inflorescences pseudoracemes of 2 heads; minor phyllode veins weakly reticulate. | A. cyclops |
14. Inflorescences pseudoracemes of 2–8 heads; minor phyllode veins prominently reticulate. | A. melanoxylon |
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