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Key to Rutaceae

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1 Herbs, becoming somewhat woody at the base, < 1 (exceptionally to 1.4) m tall; [subfamily Rutoideae].
..2 Leaves 2-pinnatifid, with many segments; [alien, grown horticulturally, scattered as persistent or weakly naturalized]
..2 Leaves simple; [native in calcareous grasslands and woodlands in ne. and c. TX westwards and southwards]
1 Shrubs and trees, definitely woody, > 1 m tall when mature (flowering and fruiting).
....3 Leaves either simple, or unifoliolate and appearing simple.
......4 Stems unarmed, inflorescence axes and young stems with short, red-brown, scurfy hairs; inflorescences of short, compact to somewhat elongate racemes; [subfamily Aurantioideae; Bergera alliance]
......4 Stems armed or unarmed, inflorescences and young stems glabrous, or pubescent with short, grey to white, erect to curved hairs; inflorescences of small fascicles, or solitary or paired flowers; [subfamily Aurantioideae; Citrus alliance].
........5 Hesperidia bluish black when ripe, 0.8-1.2 cm in diameter; stamens 10; petiole not winged; stems armed; abaxial leaf surface with raised lateral veins; petals < 0.5 cm long
........5 Hesperidia green, yellow, or orange when ripe, > 1.5 cm in diameter; stamens 20+; petiole usually winged; stems armed or unarmed; abaxial leaf surface without raised lateral veins; petals > 1 cm long
....3 Leaves pinnately or palmately compound (1-foliolate leaves sometimes also present).
..........6 Leaves 1-pinnate, either odd-pinnate and (3-) 5-19-foliolate or even-pinnate and (4-) 6-8 (-14)-foliolate.
............ 7 Leaves opposite; stems and leaves unarmed.
............ ..8 Axillary buds concealed beneath the base of the petioles on mature, leafy stems; leaflets (7-) 9-13; bark on older stems corky; [subfamily Zanthoxyloideae]
............ ..8 Axillary buds exposed above the base of the leaf petioles on mature, leafy stems; leaflets 3-9 (-11); bark on older stems smooth to somewhat rough but never corky.
............ ....9 Fruit a drupe; diameter of mid-point of internodes of leafy branches usually 1-3 mm; internode lenticels usually < 0.3 mm long, mostly round (or absent); [native in FL and TX, and also planted and escaped in FL]; [subfamily Amyridoideae]
............ ....9 Fruit of 1-5 follicles; diameter of mid-point of internodes of leafy branches usually 3-6 mm; internode lenticels usually > 0.4 mm long and round to elongate; [planted and escaped in more northern parts of our area]; [subfamily Zanthoxyloideae]
............ 7 Leaves alternate; stems and leaves either unarmed, or armed with prickles.
............ ......10 Leaflets alternate on the rachis; fruit a berry, orange to red when ripe; stems and leaves unarmed; [subfamily Aurantioideae]
............ ......10 Leaflets opposite on the rachis; stems either not armed (Glycosmis) or stems (and also often leaves) armed with prickles (Zanthoxylum, except Z. flavum).
............ ........11 Fruit a berry; [subfamily Aurantioideae]
............ ........11 Fruit of 1-5 follicles; [subfamily Zanthoxyloideae]
..........6 Leaves palmately 3-foliolate.
............ ..........12 Branches armed with axillary spines; fruit a hesperidium; [subfamily Aurantioideae].
............ ............ 13 Petiole winged; stamens 20+; hesperidia 4-5 cm in diameter, dark yellow to orange when ripe, densely pubescent, usually with > 20 seeds (looking like a small, hairy orange)
............ ............ 13 Petiole not winged; stamens 6-10; hesperidia 1-1.5 cm in diameter, glabrous, red when ripe, with 1-4 seeds; spines usually paired at nodes; petals often 3
............ ..........12 Branches unarmed; fruit a drupe, few-seeded berry, or samara.
............ ............ ..14 Fruit a drupe or few-seeded berry; [subfamily Amyridoideae]
............ ............ ..14 Fruit a samara; [subfamily Zanthoxyloideae]

Key I: woody plants with opposite, compound leaves

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1 Leaves 2-3-foliolate.
..2 Leaves 2-foliolate, with a branched tendril in the terminal position (this sometimes not developed, or withered); liana
..2 Leaves 3-foliolate, lacking tendrils; shrub, liana, or tree.
....3 Upright shrub or tree.
......4 Leaflets entire, glandular-dotted; [n. FL southwards
......4 Leaflets serrate or serrulate, not glandular-dotted; [collectively widespread].
........5 Leaflets 3-5 (-7), coarsely and jaggedly serrate, with < 5 teeth per leaflet side; fruit a schizocarp of 2 samaroid mericarps (maple “keys”)
........5 Leaflets 3, evenly serrulate, with > 10 teeth per leaflet side; fruit an inflated capsule
....3 Liana or sprawling shrub.
..........6 Flowers yellow with fused petals; stems stiff, green
..........6 Flowers either white, radially symmetrical, with separate petaloid sepals (Clematis), or blue, bilaterally symmetrical, with fused petals (Vitex).
............ 7 Leaves 3-more-foliolate; flowers white, radially symmetrical, uniseriate, with white petaloid sepals and no petals
............ 7 Leaves 1 (-3) foliolate; flowers blue, bilaterally symmetrical, biseriate, with green calyx and blue corolla
1 Leaves 4-15-foliolate.
............ ..8 Leaves palmately compound.
............ ....9 Leaflets serrate; flowers white, yellow, or red; fruit a leathery capsule, irregularly spheroidal, 2-9 cm in diameter, with 1-3 (-6) large seeds, each with a large pale hilum contrasting with the dark brown color of the rest of the seed
............ ....9 Leaflets entire; flowers blue, pink, or purple; fruit either a 4-seeded drupe, < 0.5 cm in diameter, or an elongated capsule, 8-10 cm long and ca. 0.7 cm in diameter.
............ ......10 Leaflets < 3× as long as wide, broadly rounded at the tip; fruit an elongated capsule, 8-10 cm long and ca. 0.7 cm in diameter [peninsular FL]
............ ......10 Leaflets > 4× as long as wide, acute at the tip; fruit a 4-seeded drupe, < 0.5 cm in diameter; [widespread in our region]
............ ..8 Leaves pinnately compound, bipinnately compound, or more complexly compound.
............ ........11 Plant a liana (woody vine).
............ ..........12 Leaves pinnately compound, with 7-15 coarsely serrate leaflets; perianth biseriate, with a green synsepalous calyx and an orange sympetalous corolla; fruit an elongate capsule, with many winged seeds; stems to 20 cm in diameter, with tan bark
............ ..........12 Leaves either pinnately compound, the leaflets 3-7 and coarsely serrate, or more complexly compound, the leaflets 5-many, not serrate though often lobed; perianth uniseriate, with a white, pink, or purplish aposepalous calyx and no corolla; fruit an aggregate of plumose achenes; stems to 1 cm in diameter, brown or green
............ ........11 Plant a tree or shrub, with stiff branches.
............ ............ 13 Leaves 3-7-foliolate and strictly 1-pinnate; leaflets with a few very coarse teeth; 1st year stems green; fruit a pair of winged, asymmetrical samaroid mericarps
............ ............ 13 Leaves 3-15-foliolate, 1-pinnate or partially 2-pinnate; leaflets evenly serrate with many teeth or entire; 1st year stems tan to brown (very new growth may be green); fruit either a symmetrical (winged) samara (Fraxinus) or a purplish-black, many-seeded berry (Sambucus).
............ ............ ..14 Fruit a purplish-black or red, 4-seeded berry (Sambucus); plant a shrub or small tree; stems hollow or pithy; petiole prominently grooved on the upper side; fresh leaves somewhat fleshy in texture
............ ............ ..14 Fruit either a green or tan, symmetrical (winged) samara or a blackish 5-seeded dryish drupe; plant a small to large tree; stems solid and woody; petiole nearly round in ×-section (not grooved); fresh leaves membranaceous or coriaceous in texture.
............ ............ ....15 Fruit a symmetrical samara; axillary buds suprapetiolar (though sometimes almost hidden within the strongly U-shaped petiolar attachment; [common native (also planted)]
............ ............ ....15 Fruit a nearly spherical 5-seeded dry drupe; axillary buds infrapetiolar (hidden by the swollen petiole base; [rarely escaped alien]
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