1 Leaves evergreen. {add to 1a: Glycosmis in RUTACEAE}

  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 (except C. reticulata, which sometimes lacks wings entirely), constricted at the base of the blade (except linear in C. medica)

    3 Fruit various (but not a hesperidium); petiole linear (sometimes swollen, but not flanged nor winged with leafy tissue).

      4 Leaves pubescent with stellate hairs, rufous 2-branched hairs or peltate scales (these sometimes also mixed with simple hairs), OR leaves with glandular punctae, these appearing as translucent dots (best seen on lower leaf surfaces, with at least 10x magnification).

        5 Fruit an elongate-cylindric and pendulous capsule, borne on a slender gynophore; stamens usually much longer than the broadened petals and conspicuously exerted from the flowers

        5 Fruit not as above, instead an acorn (Quercus), a subglobose to ellipsoid berry (SAPOTACEAE), or a fleshy drupe (Elaeagnus); stamens not long exerted from the flowers, or if so, then the flowers apetalous (Melaleuca).

          6 Leaves (when fresh) strongly odorous, glandular-punctate (appearing as translucent dots), with strongly parallel venation; bark on medium-aged to mature trees papery and peeling; fruit a sub-globse capsule (the hypanthium somewhat woody)

          6 Leaves (when fresh) not strongly fragrant nor bearing glandular punctae, instead with stellate hairs, rufous 2-branched hairs, or punctate scales, leaf venation various but not strongly parallel, bark various but not papery.

             7 Plants exuding milky sap (when punctured); fruit a berry, these large, subglobose and roughened on the exterior (Manilkara) or smaller and ellipsoid to ovoid in shape (Chrysophyllum); plants (leaves or elsewhere) with rufous, 2-branched hairs (strongly rufous in Chrysophyllum; if leaves strongly glaucous and glabrous, as in Manilkara jamiqui, then leaf apices clearly retuse)

               8 Sepals 4-6 (in one whorl, these all imbricate); fruit an ellipsoid to ovoid berry, purple to black when ripened, the outer surface not notably roughened; leaves (abaxially) densely rufous throughout

               8 Sepals 6 (in 2 whorls of 3, the outer whorl valvate); fruit subglobose and , the outer surface brown and roughened when ripe; leaves glabrous (glaucous and with a retuse apex) or if rufous the hairs usually concentrated along the midrib

             7 Plants not with conspicuous milky sap; fruit a drupe (Elaeagnus) or acorn (Quercus); plants with peltate scales or stellate hairs.

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

                 9 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, the hairs strictly simple (sometimes also bearing a few conspicuous apical, marginal or abaxial pit domatia in COMBRETACEAE).

                   10 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

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

                     11 Inflorescence terminal, the flowers arranged in a corymb, umbel, compound cyme, or raceme (panicle in Pittosporum and sometimes Conocarpus); fruit either a capsule (dehiscing along 1 to 5 longitudinal sutures, elongate in CAPPARACEAE) or a 1-4-seeded drupe (Bourreria; Canella; Lumnitzera).

                       12 Flowers apetalous, arranged in small spherical heads within a raceme or panicle; plants of salt-exposed coastal habitats

                       12 Flowers bearing petals; plants of various inland and coastal habitats

                          13 Plants sometimes with pneumatophores; leaf blades with apical and pit-domatia present; [non-native, s. FL]

                          13 Plants never with pneumatophores; leaf blades without pit-domatia.

                            14 Inflorescence a compound cyme; petals deep red to magenta; fruit a 1-few-seeded drupe

                            14 Inflorescence a simple corymb, umbel, or raceme (panicle in Pittosporum); petals white or pink; fruit a capsule, opening along 1, 3, or 5 sutures (or a 4-seeded drupe in Bourreria).

                              15 Fruit a drupe, the drupe bearing 4 bony nutlets with abaxial ridges; flowers white, rotate and salverform (the corolla tube evident), arranged in terminal cymes, the corolla lobes usually orbicular

                              15 Fruit a capsule (splitting along 1, 3, or 5 sutures); flowers white or pink, rotate but not salverform (lacking an evident lengthened corolla tube), arranged in terminal (or sometimes axillary) corymbs, umbels, or racemes (panicles in Pittosporum).

                                16 Capsules pendulous and conspicuously elongate-cylindric, borne on a slender gynophore; seeds few-many, contrasting sharply with the bright red capsule interior; plants shrubs or small trees, or sometimes loosely scrambling over other plants; stamens usually much longer than the petals and conspicuously exerted from the flowers

                                16 Capsules erect, not long-cylindric nor borne on a slender gynophore; capsule interior not bright red; plants shrubs or trees; stamens not conspicuously exerted past the petals.

                                  17 Ovaries 2-carpellate; capsules dehiscing along one major adaxial suture, appearing berry-like before dehiscence, the seeds often surrounded by a glutinous material

                                  17 Ovaries 5-10-carpellate; capsules dehiscing along 5 sutures.

                                    18 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

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

                     11 Inflorescence axillary, the flowers arranged in a raceme, panicle, umbel, fascicle, or sometimes flowers solitary; fruit drupaceous, fleshy to dry, but not regularly dehiscent along sutures.

                                       19 Flowers apetalous, arranged in small spherical heads within a raceme or panicle; plants of salt-exposed coastal habitats

                                       19 Flowers bearing petals, the inflorescence variously shaped (flowers occasionally solitary); plants of various inland and coastal habitats.

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

                                         20 Flowers in inflorescences of > 2 flowers (or if rarely solitary, then the perianth 5-merous); perianth not fleshy, in whorls of 4 or 5 (or 3 in Lauraceae); carpels 1, 2, 3, 4, or 5, fused (at least basally); fruit a capsule, drupe, or berry

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

                                             22 Flowers arranged in axillary spikes; leaves clustered at branch tips; stipules reduced to glandular hairs at petiole base; plants armed or unarmed; branches arranged in tiers, the main branches erect, the lateral spreading horizontally

                                             22 Flowers arranged in axillary racemes; leaves clustered apically or spaced; stipules absent or shedding and linear-lanceolate; plants unarmed; branches not arranged in conspicuous tiers.

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

                                               23 Fruit a fleshy, black, spherical drupe; stamens 10; carpels 1; leaves entire or spinose-serrate, elliptic, the apex acute to short-acuminate; stipules shedding, linear to lanceolate

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

                                                 24 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]

                                                 24 Fruit a fleshy (but not oily) 1-8-seeded drupe, a berry, or a 2-4-locular capsule; 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].

                                                    25 Leaves usually not subdistichous, the bases of the blades not oblique; flowers usually white (Ilex) or white, cream, greenish, or yellowish (Sideroxylon; Tricerma), these never present on trunks, the trunks rounded (not fluted); [collectively widespread, including FL]

                                                      26 Fruit a bright red, 2-4-locular capsule, the seeds surrounded by a bright red aril

                                                      26 Fruit a drupe or berry.

                                                        27 Plants unarmed (stems lacking armature, but the leaves bearing marginal prickles or spines); stamens 4-7, not epipetalous; fruit a drupe with 4-8 pyrenes; flowers 4-7-merous

                                                        27 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.

                                                          28 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.

                                                            29 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)

                                                            29 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)

                                                          28 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.

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

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

                                                                 31 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].

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

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

                                                                     33 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

                                                                     33 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.

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

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

                                                              30 Leaves > 1.4× as long as wide.

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

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

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

                                                                              37 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]

                                                                              37 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]

                                                                           36 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.

                                                                                38 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.

                                                                                  39 Fruit a spherical, dry drupe, 4-8 mm in diameter, with a single seed; leaf 1.5-6 cm wide

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

                                                                                38 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).

                                                                                    40 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)

                                                                                    40 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.

                                                                                      41 Leaf undersurface strongly whitened

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

                                                                                        42 Flowers unisexual and borne in male and female catkins; plants dioecious

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

                                                                                           43 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].

                                                                                             44 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

                                                                                             44 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

                                                                                           43 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].

                                                                                               45 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

                                                                                               45 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.

                                                                                                 46 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

                                                                                                 46 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.

                                                                                                   47 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

                                                                                                   47 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.

                                                                                                     48 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

                                                                                                     48 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.

                                                                                                        49 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

                                                                                                        49 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

1 Leaves evergreen.

  2 Petiole flanged or winged (except C. reticulata, which sometimes lacks wings entirely), constricted at the base of the blade; fruit a hesperidium

  2 Petiole linear (not flanged or winged with leafy tissue); fruit various.

    3 Inflorescence a thin (superficially spike-like) thyrse; leaves linear-lanceolate, the petiole apex bearing 2 glands; seeds with a red aril; [waif, Escambia County, FL]

    3 Inflorescence various, not a thyrse (if thin, then flowers arranged in catkins in FAGACEAE); leaves variously lanceolate, elliptic to ovate or rounded, the petiole apex not bearing 2 glands; seeds not bearing red arils; [widespread natives and non-natives]

      4 Leaves 7-20 cm long, usually at least some on a branch > 12 cm long, thick in texture but readily flexible when fresh.

        5 Inflorescence of a solitary flower, axillary, 5-7 cm across; fruit a capsule, ca. 1 cm in diameter

        5 Incflorescence a corymb or cyme of many, smaller flowers; fruit a pome, 0.4-0.8 (-1.2) cm in diameter (Photinia) or a drupe of similar size (Ehretia).

          6 Fruit an orange to yellow drupe, ultimately containing 4 seeds (from 2 paired nutlets); inflorescence a cyme

          6 Fruit a pome; inflorescence a corymb

      4 Leaves 3-12 cm long, thick in texture and also noticeably stiff.

             7 Leaves subdistichous or not, the bases of the blades not oblique; flowers variously colored (usually white in Ilex and Ehretia, brownish-white and apetalous in Fagaceae); plants never cauliflorous, the trunks smooth or with thickened ridges, rarely fluted.

               8 Leaf with a spinose margin, the marginal spines well-developed, generally arrayed along most of the leaf margin and borne at nearly a right angle to the midvein; flowers not catkins, bearing petals; fruit berrylike, usually at least somewhat fleshy

               8 Leaf margins serrate with one or a few stiff teeth (sometimes sharpish, but not spines), these usually towards the apex of the leaf and oriented somewhat ascendant; flowers catkins and apetalous (FAGACEAE) or bearing petals (Ehretia in EHRETIACEAE); fruit an acorn (not fleshy) or a drupe (somewhat fleshy).

                 9 Flowers bearing petals, arranged in cymes; fruit a drupe, usually at least somewhat fleshy

                 9 Flowers catkins, apetalous; fruit an acorn, not fleshy

1 Leaves deciduous.

                   10 Secondary veins neatly pinnate, the veins on each side of the midrib evenly spaced, parallel to one another, and extending nearly or actually to the leaf margin; fruit either a 1-seeded nut (dry, with or without samaroid wings, bracts, a subtending cupule, or an enclosing and valvate involucre) or a fleshy drupe with 2-4 stones.

                     11 Leaves doubly-serrate, the number of teeth greater than the number of the pinnate secondary veins (sometimes obscurely so in Planera in ULMACEAE); fruit a nut or samaroid nut, lacking a cupule or valvate involucre, though sometimes associated with green, leaf-like bracts.

                       12 Flowers unisexual, in catkins, the tree monoecious; leaf base symmetrical

                       12 Flowers bisexual, in axillary fascicles, the tree androgynous; leaf base strongly asymmetrical (oblique) or nearly or quite symmetrical.

                     11 Leaves singly serrate or crenate, the teeth the same number as the secondary veins; fruit either a fleshy drupe with 2-4 stones, or a nut with a cupule (acorn) or enclosed by a valvate involucre that splits at maturity.

                          13 Fruit a fleshy drupe with 2-4 stones

                          13 Fruit dry, single-seeded (or with 1-4 nuts in Castanea).

                            14 Fruit > 9 mm long or wide, either a nut with a cupule (acorn) or 1-4 nuts enclosed by a valvate involucre that splits at maturity

                            14 Fruit < 9 mm long and wide, leathery, indehiscent, winged or not

                   10 Secondary veins not as above, usually arching and/or branching or reticulating well before reaching the leaf margin; fruit various.

                              15 Leaves strongly 3-5-veined from the base; leaf blade cordate or truncate, usually oblique.

                                16 Inflorescence terminal, a compound cyme; peduncles and pedicels becoming swollen, fleshy, and juicy at maturity; [plant rarely naturalized]

                                16 Inflorescence axillary, a solitary flower, a fascicle or cluster, or a cyme; peduncles and pedicels remaining stalk-like; [collectively widespread and common].

                                  17 Flowers unisexual, plants monoecious; bark on mature trees usually warty or with corky fissures; pith of mature twigs chambered with hollow sections between soft partitions (Celtis) or solid (Trema).

                                    18 Leaf blades entire or irregularly serrate (the margins usually with at least some portions entire, even if minimal), the lower surfaces glabrous or nearly so; cymes few-flowered (at least pistillate); [collectively widespread]

                                    18 Leaf blade margins uniformly serrate or crenate throughout (the teeth uniform and without some portions entire), the lower surfaces pubescent; flowers many (12-20), arranged in dense axillary cymes; [FL and s. TX only in our area]

                                  17 Flowers bisexual; plants hermaphroditic; pith of mature twigs continuous without hollow sections between partitions.

                                       19 Flowers white, showy, and often singular (the petals 12-20 mm long); fruit a red berry 10-15 mm in diameter; [uncommon non-native, s. FL]

                                       19 Flowers either smaller yellowish-white cymes (Tilia) or unisexual pistillate heads or staminate catkins (Moraceae); fruit either nutlike and bearing a curved bract (Tilia) or a fleshy syncarp (Moraceae); [widespread native and non-natives]

                                         20 Flowers bisexual; inflorescence an axillary cyme; fresh leaves and stems lacking white latex; fruit simple, a 1-seeded nut; main leaf veins splitting several times towards the leaf margin and leading into the teeth without rejoining and forming a marginal vein; basal veins 5, palmate, all joining together at the summit of the petiole; main lateral leaf veins (above the basal veins) often opposite; winter buds with 3 entire bud scales (1 much smaller than the other 2)

                                         20 Flowers unisexual, the pistillate inflorescence a head, the staminate inflorescence a catkin, borne on the same tree (monoecious) or on separate trees (dioecious); fresh leaves and stems with white latex; fruit a multiple of fleshy achenes; main leaf veins splitting towards the margin but then rejoining to form a prominent, looping (scalloped) marginal vein; basal veins 3, palmate, sometimes an additional prominent vein on each side joining the lateral vein above its divergence from the petiole end; main lateral leaf veins (above the basal veins) mainly alternate; winter buds with 5 ciliate-margined bud scales

                              15 Leaves pinnately veined; leaf blade base cordate, subcordate, truncate, rounded, or cuneate base, not oblique.

                                           21 Inflorescence a terminal raceme of racemes, with more than 50 flowers; petals connate, urceolate; fruit a 5-valved capsule, < 6 mm in diameter; fresh leaves with a sour taste

                                           21 Inflorescence various, either with < 30 flowers or if with > 50 flowers a catkin (with a single axis); corolla with separate petals (or petals absent); fruit various, fleshy or dry, if a 5-valved capsule (Franklinia in THEACEAE), then 15-20 mm in diameter; fresh leaves without a sour taste.

                                             22 Pubescence stellate (look especially in vein axils on the undersurface of the leaf)

                                             22 Pubescence simple (or absent).

                                               23 Flowers very large and showy, 7-9 cm across; fruit a subglobose capsule 1.5-2 cm in diameter

                                               23 Flowers less than 2 cm across; fruit either fleshy and indehiscent, a drupe, samara, or pome, or dry and dehiscent, an ovoid or lanceolate capsule < 0.7 cm in diameter.

                                                 24 Flowers unisexual, borne either in axillary catkins; trees dioecious; fruit either dehiscent, a lanceoloid or ovoid capsule (SALICACEAE) or indehiscent, a samara (Eucommia ulmoides).

                                                    25 Plants bearing latex; fruit a samara, 25-32 mm long, the apex emarginate

                                                    25 Plants not bearing latex; fruit a lanceoloid or ovoid capsule

                                                 24 flowers bisexual (unisexual in Ilex in AQUIFOLIACEAE), borne variously in terminal or axillary clusters, cymes, racemes, or umbels, but not at all catkin-like; trees hermaphroditic (dioecious in AQUIFOLIACEAE); fruit indehiscent, a fleshy drupe or pome with 1-many seeds.

                                                      26 Pith of twigs with transverse diaphragms and also continuous between the diaphragms (make a longitudinal section of twig and use at least 10× magnification; look for translucent diaphragms spaced at < 1 mm apart, with whiter pith tissue between them); fruit distinctly longer than broad, a 1-seeded drupe

                                                      26 Pith of twigs lacking diaphragms, continuous and homogeneous; fruit either suborbicular to spherical or pear-shaped, either a several- to many-seeded pome, or a berry-like drupe with 4-8 seeds, or a 1-seeded drupe.

                                                        27 Vascular bundle scars 1 in each leaf scar; fruit a berrylike drupe with 4-8 bony pyrenes; ovary superior, the calyx persistent at the base of the fruit

                                                        27 Vascular bundle scars (2-) 3 in each leaf scar; fruit a pome or 1-seeded drupe; ovary either inferior and the calyx persistent at the summit of the fruit (Amelanchier, Crataegus, Malus, Pyrus) or superior and the calyx not at all persistent at the base of the fruit (Prunus)