1 Branches armed with nodal thorns, (1-) 5-20 (-55) mm long.

..2 Thorns usually single, usually < 8 mm long and rarely bearing leaves; styles 3-4.5 mm long; fruit 7-12 mm in diameter; pyrene 5-7 mm long, coarsely reticulate

..2 Thorns usually paired, often > 10 mm long and then often bearing leaves; styles < 1 mm long; fruit 6-7 (-8) mm in diameter; pyrene to 4 mm long, with low, alveolate-reticulate sculpturing

1 Branches unarmed.

....3 Leaves thick, very glossy above; bark remaining smoothish, lacking protuberances; [rare exotic]

....3 Leaves thin, dull or glossy above (glossy normally only in sun leaves); bark developing wartlike corky protuberances on larger individuals; [collectively common natives].

......4 Leaf lower surface densely white-pubescent; [TX]

......4 Leaf lower surface glabrous or with inconspicuous hairiness mainly on the veins; [collectively widespread].

........5 Leaf blades (fully-formed leaves subtending fruits) 7-12 cm long, the longer side with 23-40 teeth, the shorter with 12-27 teeth; secondary veins 5-8 on each side of the midvein, the basalmost reaching the leaf margin at a point 1/3 to ½ the length of the leaf above the base; fruits 8-10 mm long

........5 Leaf blades (fully-formed leaves subtending fruits) 2.0-8.5 cm long, each side with 0-15 (-23?) teeth; secondary veins 3-5 on each side of the midvein, the basalmost reaching the leaf margin at a point 1/3 to 2/3 the length of the leaf above the base; fruits 5-10 mm long.

..........6 Leaf blades 2-4.5 (-7) cm long; upper leaf surface harshly scabrous; leaf apex obtuse to acute (rarely nearly acuminate); fruit (5-) 8-10 mm in diameter; [LA and OK southwestwards]

..........6 Leaf blades (2-) 5-8 (-15) cm long; upper leaf surface smooth or slightly scabrous; leaf apex acuminate to acute; fruit 5-8 mm in diameter; [collectively widespread].

............ 7 Plants shrubs or small trees, to 7 m tall, with ascending trunks and horizontal or arching leaders; bark often nearly smooth (sometimes with corky warts near the base or around wounds); leaf undersurface glaucous or pale green, usually distinctly lighter than the upper surface; flower stalks usually hairy (puberulent); twigs usually moderately to densely hairy (sometimes glabrous); anthers small and indehiscent, pollen malformed and generally sterile (< 10% of the grains stainable with acetocarmine)

............ 7 Plants usually trees, to 30 m tall, typically single-trunked, with erect leaders; bark with corky warts on trunks and major branches; leaf undersurface usually bright green, little if at all paler than the uppersurface; flower stalks glabrous (rarely with a few hairs); twigs glabrous or sparsely hairy; anthers well-developed, dehiscent, pollen copious, regular, and fertile (> 95% of the grains stainable with acetocarmine).

............ ..8 Leaves subtending fruits with margins with 2-15 teeth 1-2 mm long on each side

1 Leaves evergreen. {add to 1a: [Conocarpus] COMBRETACEAE; [Maytenus] CELASTRACEAE}

..2 Leaves tiny, scale-like, broadest at the base and more or less clasping the stem, < 10 mm long and < 1 mm wide

..2 Leaves larger and broader, > 40 mm long and > 8 mm wide.

....3 Fruit a hesperidium; petiole flanged or winged for most of its length, constricted at the base of the blade (except linear in C. medica)

....3 Fruit various (but not a hesperidium); petiole linear (not flanged or winged with leafy tissue).

......4 Leaves pubescent with stellate hairs or peltate scales (sometimes hairs simple), or glandular punctate, appearing as translucent dots (best seen on lower leaf surfaces, with at least 10x magnification).

........5 Leaves (fresh) strongly odorous, glandular-punctate (appearing as translucent dots), with strongly parallel venation; bark on medium-aged to mature trees papery and peeling

........5 Leaves (fresh) not strongly fragrant, with stellate hairs or punctate scales, leaf venation various but not strongly parallel, bark various but not papery

..........6 Vestiture of the lower leaf surface of silvery and/or reddish peltate scales; plants hermaphroditic, the flowers bisexual; fruit a fleshy drupe

..........6 Vestiture of the lower leaf surface in part of stellate hairs (and also of simple acicular hairs and gland-tipped hairs); plants monoecious, the male flowers in yellow to brownish catkins, the female flowers solitary or in small spikes; fruit a nut in a cupule (an acorn)

......4 Leaves glabrous, or if hairy, with strictly simple hairs.

............ 7 Flowers solitary, terminal, large (> 5 cm in diameter); pistils many, carpels separate; petals many (typically > 8); leaves mostly > 10 cm long (at least some on a branch longer than 10 cm); fruit an aggregate of follicles, each dehiscing along 1 suture; stipule scar circumferential at each node, encircling the twig

............ 7 Flowers either in axillary racemes, panicles, umbels, fascicles, or solitary, or in terminal corymbs, umbels, compound cymes, or racemes, small (< 5 cm in diameter); pistil 1, with 1-8 fused carpels; petals 3-8; leaves < 30 cm long; fruit either a drupe, berry, or capsule; stipule scars either absent or linear or triangular, not circumferentially encircling the twig.

............ ..8 Inflorescence terminal, a corymb, umbel, compound cyme, or raceme; fruit either a capsule (dehiscing along 5 longitudinal sutures) or a few-seeded berry.

............ ....9 Inflorescence a compound cyme; petals deep red to magenta; fruit a few-seeded drupe

............ ....9 Inflorescence a corymb, umbel, or raceme; petals white or pink; fruit a capsule, opening by 5 longitudinal sutures.

............ ......10 Capsules ovoid to globose or subglobose, about as long as broad, 5-8 mm long; leaves 5-12 cm long, 2-3× as long as wide

............ ......10 Capsules elongate, > 2× as long as broad, 8-18 mm long; leaves 10-30 cm long, 3-5× as long as wide

............ ..8 Inflorescence axillary, a raceme, panicle, umbel, fascicle, or solitary; fruit drupaceous, fleshy to dry, but not regularly dehiscent along sutures.

............ ........11 Flowers solitary, axillary or superaxillary; perianth somewhat fleshy, in whorls of 3; carpels numerous, partly fused; fruit an aggregate syncarp

............ ........11 Flowers in inflorescences of > 2 flowers; perianth not fleshy, in whorls of 4 or 5 (or 3 in Lauraceae); carpels 2, 3, 4, or 5, fused; fruit a capsule, drupe, or berry

............ ..........12 Inflorescence an axillary raceme (with an elongate central axis, to which all flowers/fruits are attached).

............ ............ 13 Fruit a dry, tan to brown, spherical or winged drupe; stamens 5 or 10; carpels 2-5; leaves oblanceolate (rarely narrowly elliptic), < 2.5 cm wide, the apex obtuse (more rarely acute, retuse, or rounded)

............ ............ 13 Fruit a fleshy, black, spherical drupe; stamens 10; carpels 1; leaves elliptic, the apex acute to short-acuminate

............ ..........12 Inflorescence either an axillary umbel or fascicle (or reduced to solitary) or an axillary compound inflorescence (panicle or compound cyme), with 2-3 orders of branching.

............ ............ ..14 Fruit a fleshy and oily 1-seeded drupe; flowers 3-merous, with separate and undifferentiated perianth segments; fresh plants strongly aromatic; inflorescence compound, a panicle or compound cyme (with 2-3 orders of branching); [Basal Angiosperms]

............ ............ ..14 Fruit a fleshy but not oily 1-8-seeded drupe or berry; flowers 4-8-merous, with differentiated sepals and petals, the petals usually basally fused; fresh plants not strongly aromatic; inflorescence an axillary umbel or fascicle (or reduced to solitary), a central axis absent or < 1 cm long; [Eudicots].

............ ............ ....15 Plants unarmed (or with marginal leaf prickles or spines); stamens 4-7, not epipetalous; fruit a drupe with 4-8 pyrenes;flowers 4-7-merous

............ ............ ....15 Plants armed with nodal thorns; stamens 5 and staminodia 5, epipetalous; fruit a berry or drupe with 1 seed;flowers 5-merous

1 Leaves deciduous.

............ ............ ......16 Leaf base deeply to shallowly cordate, with 3-7 palmate veins from the base; leaf blade about as wide as long or a little longer, mostly 0.9-1.3× as long as wide.

............ ............ ........17 Juncture of petiole and leaf blade with 2 red glands; corolla radially symmetrical, with 5-8 petals, white with red veins towards the base of the petals; flowers unisexual; fruit globose, 4-8 cm in diameter; main palmate leaf veins 3 (-5)

............ ............ ........17 Juncture of petiole and leaf blade eglandular, but the uppermost 1-3 mm of the petiole swollen into a prominent upper pulvinus; corolla bilaterally symmetrical, with 5 petals, pink to purple (rarely white in some cultivars); flowers bisexual; fruit an oblong, flat legume, 6-10 cm long; main palmate leaf veins 5-7 (-9)

............ ............ ......16 Leaf base cuneate, rounded, truncate, subcordate, or auriculate (with 2 small “earlobe-like” lobes at the base of the leaf blade), with 1 (mid) vein from the base (3 veins from the base in Celtis in CANNABACEAE); leaf blade about as wide as long, or somewhat to much longer, 0.9-10× as long as wide.

............ ............ ..........18 Leaves 0.9-1.4× as long as wide (some taxa keyed in both leads).

............ ............ ............ 19 Stipule scars circumferential, forming a line around the twig; flowers and aggregate fruits solitary, terminal; [Basal Angiosperms]

............ ............ ............ 19 Stipule scars not circumferential (or not apparent); flowers and simple fruits in inflorescences of 1-many flowers, axillary or terminal, but not simultaneously solitary and terminal; [Eudicots].

............ ............ ............ ..20 Leaf blade 3-6 cm long, 1-1.5× as long as the flexuous petiole

............ ............ ............ ..20 Leaf blade 4-30 cm long, > 3× as long as the stiff petiole.

............ ............ ............ ....21 Petioles 1-5 (or more) cm long; leaves broadly orbicular, rounded at the base, usually rounded (rarely obtuse or nearly acute) at the apex, entire; hairs on foliage simple or absent; fruit a fleshy drupe

............ ............ ............ ....21 Petioles < 1 cm long; leaves various in shape, often acuminate at the apex and/or cuneate at the base, often with some tendency to toothing; hairs on foliage stellate (use at least 10× magnification), at least in part; fruit either a nut borne in a cup (acorn) or a dry, subglobose 3-valved capsule, with 1 seed.

............ ............ ............ ......22 Fruit a nut in a cupule (an acorn); flowers unisexual, greenish or brownish, individually inconspicuous, the male flowers borne in catkins

............ ............ ............ ......22 Fruit a dry, subglobose 3-valved capsule, with 1 seed; flowers bisexual, white, conspicuous

............ ............ ..........18 Leaves > 1.4× as long as wide.

............ ............ ............ ........23 Leaves densely covered with silvery peltate scales (use 10× or greater magnification), giving the leaf blade surface a metallic appearance

............ ............ ............ ........23 Leaves glabrous, glabrescent or variously pubescent (including densely and silkily so, giving the leaf surface a shiny appearance), but not as above.

............ ............ ............ ..........24 Plants bearing nodal thorns; leaves elliptic to obovate, 3-9 cm long, 1-4 cm wide, 1.5-4× as long as wide.

............ ............ ............ ............ 25 Sap clear, not viscous; sepals 4; petals 4, densely long-hairy on their upper (inner) side); fruit a yellow, 1-seeded drupe, 20-30 mm long; [FL southward]

............ ............ ............ ............ 25 Sap milky or nearly clear but thick and sticky; sepals 5; petals 5, not densely long-hairy; fruit a black, 5-seeded berry, 5-15 mm long; [widespread in our area]

............ ............ ............ ..........24 Plants unarmed (except spiny in Maclura in MORACEAE); leaves various in shape, from broadest towards the base, near the middle, or towards the apex, 3-80 cm long, 1-30 cm wide, 1.5-10× as long as wide.

............ ............ ............ ............ ..26 Leaves distinctly widest near the base (at a point < 0.3× of the way from the base of the leaf blade to its apex), gradually long-tapering to an acuminate apex.

............ ............ ............ ............ ....27 Fruit a spherical, fleshy multiple, 80-120 mm in diameter; leaf 5-8 cm wide

............ ............ ............ ............ ..26 Leaves widest near the middle or towards the tip of the leaf blade (at a point > 0.4× of the way from the base of the leaf blade to its apex).

............ ............ ............ ............ ......28 Pubescence of the foliage stellate (at least in part; simple hairs sometimes present as well); flowers unisexual, the individual flowers inconspicuous, male flowers in catkins; fruit a nut in a cupule (an acorn)

............ ............ ............ ............ ......28 Pubescence of the foliage simple or absent (except stellate in STYRACACEAE); flowers bisexual, conspicuous, borne variously, but not in catkins (except in Leitneria); fruit various.

............ ............ ............ ............ ........29 Leaf undersurface strongly whitened

............ ............ ............ ............ ........29 Leaf surface green (often somewhat paler green than the upper surface, but not whitened).

............ ............ ............ ............ ..........30 Flowers unisexual and borne in male and female catkins; plants dioecious

............ ............ ............ ............ ..........30 Flowers bisexual, not borne in catkins; plants hermaphroditic.

............ ............ ............ ............ ............ 31 Flowers solitary; ovary superior; perianth either 3-merous and whorled or many-merous and spiraled; leaves mostly > 20 cm long and > 8 cm wide, distinctly broadest towards the apex (> 0.6× of the way from the leaf blade base to apex) (except Magnolia acuminata, which is sometimes both shorter, narrower, and broadest near the middle or towards the base); [Basal Angiosperms].

............ ............ ............ ............ ............ ..32 Flowers axillary, < 2 cm across, brown or maroon; perianth 3-merous, whorled; fresh foliage with a strong musky odor; fruit a fleshy berry; leaves cuneate at the base; twigs lacking circumferential stipule scars at each node

............ ............ ............ ............ ............ ..32 Flowers terminal, > 4 cm across, white, pale yellow, or pink; perianth many-merous, spiraled; fresh foliage not noticeably aromatic; fruit an aggregate of follicles; leaves cuneate or auriculate at the base; twigs with circumferential stipule scars at each node

............ ............ ............ ............ ............ 31 Flowers in inflorescences of several to many; ovary inferior (or superior in Diospyros in EBENACEAE and Cyrilla in CYRILLACEAE); perianth 4-5-merous; leaves mostly < 20 cm long and < 10 cm wide, broadest near the middle or towards the apex; [Eudicots].

............ ............ ............ ............ ............ ....33 Leaves with prominently parallel-arcing secondary veins; inflorescence a terminal corymb; leaves clustered at the tips of the twigs, thus appearing pseudo-whorled; trichomes of the leaf undersurface predominantly 2-branched (some simple) (use at least 10× magnification); flowers 4-merous; fruit a blue drupe; small tree

............ ............ ............ ............ ............ ....33 Leaves with secondary veins more obscure and complexly branching into tertiary veins; inflorescence axillary (often on the previous year’s wood), solitary to variously fascicled, clustered, or in racemes; leaves arrayed distichously along horizontal or arching twigs, not prominently clustered or pseudo-whorled (except often in Cyrilla in CYRILLACEAE, Symplocos in SYMPLOCACEAE, and Nyssa in NYSSACEAE); trichomes of the leaf undersurface either simple or stellate (or absent); flowers 4-5-merous; fruit a green, blue, or black drupe, an orange berry, or a green to brownish indehiscent capsule; small to large tree.

............ ............ ............ ............ ............ ......34 Pubescence of foliage and other parts stellate (use at least 10× magnification); petals 4-5, white, 10-25 mm long; fruit dryish, indehiscent, either longitudinally 2-4-winged or not winged

............ ............ ............ ............ ............ ......34 Pubescence of foliage and other parts simple; petals either 0, or 4-5 and pink, white, or greenish-yellow, or 10 and greenish-yellow; fruit either a somewhat to very fleshy drupe or berry or a dry, brownish, spherical drupe, 2-2.5 mm in diameter.

............ ............ ............ ............ ............ ........35 Leaves < 2.5 cm wide, dark green above, somewhat thickened, and tardily deciduous or semi-evergreen; fruit a dry, brownish, spherical drupe, 2-2.5 mm in diameter; inflorescence a narrowly cylindrical raceme with > 40 flowers

............ ............ ............ ............ ............ ........35 Leaves > 2.5 cm wide, usually medium-green above, herbaceous in texture, promptly seasonally deciduous; fruit a somewhat to very fleshy drupe or berry, > 5 mm in diameter; inflorescence a solitary flower or cluster, head, or irregular raceme of < 15 flowers.

............ ............ ............ ............ ............ ..........36 Fruit a drupe (green when ripe), cylindrical to barrel-shaped, 8-12 mm long; leaves rather thick and leathery in texture, persistent into the winter, dropping tardily or at latest the following spring; flowers bisexual; stamens 30-50, in 5 fascicles

............ ............ ............ ............ ............ ..........36 Fruit a berry (orange when ripe) or a drupe (blue-black, yellow, orange, or red when ripe), 8-50 mm long, spherical or ovoid to ellipsoid; leaves thin in texture, promptly deciduous in the autumn; flowers functionally unisexual; stamens 5-16, separate.

............ ............ ............ ............ ............ ............ 37 Fruit a spherical berry, 15-50 mm long, orange when ripe, subtended by the enlarged and persistent woody or leathery calyx; vascular bundles 1 per leaf scar; leaves never toothed; leaves whitish-green beneath; leaf midrib and upper petiole with tiny glands on their upper surfaces (reddish initially, then darkening) (use at least 10× magnification); leaves glabrate to tomentose with curly hairs beneath; female and male flowers on separate trees (dioecious); stamens 16; widest point of the leaf usually at the middle or below, the apex acute to acuminate

............ ............ ............ ............ ............ ............ 37 Fruit an ovoid or ellipsoid drupe, 8-30 -40 mm long, blue-black, yellow, orange, or red when ripe; vascular bundles 3 per leaf scar; leaves sometimes bearing a few irregular teeth; leaves pale to medium green beneath; leaf midrib and upper petiole lacking reddish to dark glands on their upper surfaces; leaves glabrous or glabrate beneath; female and male flowers on the same tree (monoecious); stamens 5-12; widest point of the leaf usually beyond or at the middle, the apex obtuse to strikingly and abruptly acuminate