Keys to Dicotyledon Families
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Scott A. Mori

KEY 2. HERBACEOUS TERRESTRIAL OR AQUATIC MAGNOLIOPSIDA
KEY TO SUBKEYS

(If your plant does not key out here and is woody at the base, try the key to shrubs)


1. Leaves compound SUBKEY 1. COMPOUND LEAVES
1. Leaves simple. 2
2. Leaves opposite or whorled
 SUBKEY 2. SIMPLE OPPOSITE OR WHORLED LEAVES
2. Leaves alternate.
 SUBKEY 3. SIMPLE ALTERNATE LEAVES

KEY 2. HERBACEOUS TERRESTRIAL OR AQUATIC MAGNOLIOPSIDA
SUBKEY 1. COMPOUND LEAVES


1. Leaves trifoliolate. Stamens not tetradynamous. 2
1. Leaves pinnately divided. Stamens tetradynamous. Brassicaceae
2. Stipules present. Flowers zygomorphic. Fruits specialized legumes (loments), i.e. contracted between seeds
 Fabaceae (Desmodium)
2. Stipules absent. Flowers actinomorphic. Fruits capsules.
 Oxalidaceae

KEY 2. HERBACEOUS TERRESTRIAL OR AQUATIC MAGNOLIOPSIDA
SUBKEY 2. SIMPLE OPPOSITE OR WHORLED LEAVES


1. Leaves whorled. Flowers in dense spikes, apetalous. Piperaceae (Peperomia)
1. Leaves opposite. Flowers not in dense spikes, petals present or absent. 2
2. Plants with milky exudate.
 3
2. Plants without milky exudate.
 5
3. Leaves <2 cm long. Flowers unisexual, numerous, congested in leaf axils, in specialized cups called cyathia; peduncle not developed; ovary with 3 carpels. Euphorbiaceae (Euphorbia pro parte)
3. Leaves >2 cm long. Flowers bisexual, solitary or, if numerous, not congested, not in cyathia; peduncule developed; ovary with 2 carpels. 4
4. Leaves <5 cm long, rounded-apiculate at apex. Corolla fused into long tube; stamens and pistil not fused into column; pollen not in pollinia.
 Apocynaceae
4. Leaves >5 cm long, long attenuate, not apiculate at apex. Corolla not fused into long tube; stamens and pistil fused into column; pollen in pollinia.
 Asclepiadaceae
5. Flowers with petals not fused into distinct tube. 6
5. Flowers with petals fused into distinct tube (the lobes of the corolla may sometimes be longer than the tube, e.g., Cououbea in the Gentianaceae). 12
6. Leaves mostly in basal rosette but stem leaves opposite, with pungent aroma when crushed, the margins markedly serrate. Inflorescences cylindric, subtended by whorled bracts.
 Apiaceae (Eryngium)
6. Leaves not in basal rosette, without pungent aroma when crushed, the margins not markedly serrate. Inflorescences not cylindric nor subtended by whorled bracts.
 7
7. Leaf blades cordate. Placentation free-central. Caryophyllaceae (Drymaria)
7. Leaf blades not cordate. Placentation not free-central. 8
8. Perianth biseriate; petals conspicuous; ovary with >1 ovule.
 9
8. Perianth uniseriate; tepals inconspicuous; ovary with 1 ovule.
 11
9. Leaf blades with arcuate secondary veins and characteristic ladder-like tertiary veins between the secondary veins. Flowers actinomorphic. Melastomataceae
9. Leaf blades without above venation. Flowers zygomorphic. 10
10. Leaves often heteromorphic, one leaf of node much larger than other. Flowers perigynous; petals magenta; placentation axile.
 Lythraceae
10. Leaves not heteromorphic. Flowers hypogynous; petals not magenta; placentation parietal.
 Violaceae (Hybanthus)
11. Leaves without stipules. Flowers bisexual, subtended by scarious bracts; filaments at least partially connate; pollen not released explosively at anthesis. Amaranthaceae
11. Leaves with stipules. Flowers unisexual, not subtended by scarious bracts; filaments not connate; pollen released explosively at anthesis. Urticaceae (Laportea & Pilea)
12. Flowers mostly actinomorphic (zygmorphic flowers may occur around outside of head in the Asteraceae).
 13
12. Flowers all zygomorphic.
 17
13. Flowers congested into heads subtended by numerous, overlapping bracts (phyllaries); calyx modified into hairs, scales, or bristles (pappus); ovary inferior. Fruits cypselas. Asteraceae
13. Flowers not congested into heads or, if in capitula, subtended by only two bracts (e.g., species of Psychotria); calyx not modified into pappus; ovary superior or inferior. Fruits not cypselas. 14
14. Ovary inferior.
 Rubiaceae
14. Ovary superior.
 15
15. Leaves often in verticils of 3, the leaf blades glandular-punctate. Corolla with lobes longer than tube; stamens 4. Scrophulariaceae (Scoparia)
15. Leaves opposite, the leaf blades not glandular-punctate. Corolla with lobes shorter than tube; stamens 5. 16
16. Stipules or stipule scars present. Inflorescences secund. Fruits either bilobed or with rough exterior.
 Loganiaceae
16. Stipules absent. Inflorescences not secund. Fruits neither bilobed nor with rough exterior.
 Gentianaceae
17. Crushed leaves often aromatic. Ovaries with single ovule per locule, the ovary often lobed at summit. Fruit often splitting into 1-seeded portions. 18
17. Crushed leaves not aromatic. Ovaries with numerous ovules per locule, the ovary never lobed at summit. Fruits never splitting into 1-seeded portions. 19
18. Flowers in capitula or, if not in capitula, the calyx with distinct protuberance; corolla markedly zygomorphic; style gynobasic. Fruits of 4 nutlets.
 Lamiaceae
18. Flowers not in capitula and calyx without protuberance; corolla slightly zygomorphic; style terminal. Fruits not of 4 nutlets.
 Verbenaceae
19. Leaves often with cystoliths on adaxial surface, these appearing as small protuberances or streaks. Flowers often, but not always, subtended by conspicuous bracts. Fruits fiddle- or club-shaped. Seeds without endosperm. Acanthaceae
19. Leaves without cystoliths. Flowers not subtended by conspicuous bracts. Fruits not fiddle- or club-shaped. Seeds with endosperm. 20
20. Leaf blades cordate, <15 mm long. Flowers purple, <10 mm long.
 Scrophulariaceae
20. Leaf blades not cordate, >15 mm long. Flowers not purple, usually >10 mm long.
 21
21. Plants of open, sunny areas. Leaf blade margins entire. Stamens 5, the anthers not connivent. Gentianaceae (Irlbachia)
21. Plants of shaded areas. Leaf blade margins dentate to serrate. Corollas white or yellow; stamens 4, the anthers connivent. Gesneriaceae

KEY 2. HERBACEOUS TERRESTRIAL OR AQUATIC MAGNOLIOPSIDA
SUBKEY 3. SIMPLE ALTERNATE LEAVES


1. Plants with milky exudate. 2
1. Plants without milky exudate. 4
2. Milky exudate sparse, not conspicuous from broken petiole. Flowers congested in heads, subtended by a series of overlapping bracts (involucre). Calyx modified into hairs. Fruits cypselas.
 Asteraceae (Emilia)
2. Milky exudate abundant, conspicuous from broken petiole. Flowers not congested in heads, not subtended by a series of overlapping bracts. Calyx not modified into hairs. Fruits berries or capsules.
 3
3. Flowers bisexual, not in cyathium; corolla red or deep pink, with petals fused into tube; anthers connivent; ovary inferior, bilocular. Fruits berries. Campanulaceae
3. Flowers unisexual, situated within a cyathium; corolla not red or deep pink, the petals not fused into tube; anthers not connivent; ovary superior, trilocular. Fruits capsules. Euphorbiaceae
4. Ovaries inferior.
 5
4. Ovaries superior.
 6
5. Leaves without stipules. Flowers congested in capitula, subtended by a series of overlapping bracts (involucre). Calyx modified into hairs, bristles, or scales (pappus); corolla with petals fused into tube. Fruits cypselas, not winged. Asteraceae
5. Leaves with stipules. Flowers not congested in capitula nor subtended by overlapping bracts. Calyx not modified into pappus; corolla with petals free. Fruits capsules, winged. Begoniaceae
6. Plants aquatic.
 7
6. Plants not aquatic.
 9
7. Submersed leaves lettuce-like. Flowers apetalous. Podostemaceae
7. Submersed leaves not lettuce-like. Flowers with tepals or petals. 8
8. Cauline leaves simple, not lobed at base, the basal leaves pinnately compound. Flowers <10 mm diam.; sepals and petals distinct; petals 4; stamens 6.
 Brassicaceae
8. All leaves simple, deeply lobed at base. Flowers >50 mm diam.; sepals and petals (tepals) not distinct; stamens numerous.
 Nymphaeaceae
9. Flowers zygomorphic (weakly zygomorphic in Petiveria). 10
9. Flowers actinomorphic. 13
10. Corolla with 4 petals. Fruits with downward curved spines at apex, epizoochorous.
 Phytolaccaceae (Petiveria)
10. Corolla with 5 petals or lobes. Fruits without downward curved spines at apex, not epizoochorous.
 11
11. Flowers with a spurred petal; ovary unilocular, with parietal placentation. Violaceae (Noisetia)
11. Flowers without a spurred petal; ovary bilocular, with axile placentation. 12
12. Leaf blades with entire margin. Corolla polypetalous, usually violet.
 Polygalaceae (Polygala)
12. Leaf blades with serrate margin. Corolla gamopetalous, white.
 Scrophulariaceae (Capraria)
13. Petals fused into tube (gamopetalous). 14
13. Petals not fused into tube (choripetalous). 15
14. Inflorescence secund. Corolla with narrow tube. Fruits not surrounded by inflated calyx, splitting into 4 parts at maturity.
 Boraginaceae
14. Inflorescence not secund. Corolla with broadly spreading tube. Fruits surrounded by inflated calyx, not splitting into 4 parts at maturity.
 Solanaceae (Physalis)
15. Stipules persistent, distinctly ciliate, some cilia nearly as long as stipule. Staminodia dimorphic, the outer numerous, filiform, the inner 5, petaloid. Ochnaceae (Sauvegesia)
15. Stipules not as above. Staminodia absent or not as above. 16
16. Leaf blades oblong, <10 mm × 4 mm. Flowers in leaf axils.
 Euphorbiaceae (Phyllanthus)
16. Leaf blades not oblong, >10 mm × 4 mm. Flowers in racemes or spikes.
 17
17. Leaves with stellate pubescence. Stamens fused into tube (monadelphous). Fruits splitting into individual units (mericarps), these with pointed apices, epizoochorous. Malvaceae (Pavonia)
17. Leaves glabrous or with simple pubescence. Stamens not fused into tube. Fruits not as above. 18
18. Plants with stinging hairs. Leaf blades with markedly dentate margins.
 Urticaceae (Laportea)
18. Plants without stinging hairs. Leaf blades with entire margins.
 19
19. Inflorescences spikes. Flowers apetalous; ovary unilocular. Piperaceae (Peperomia)
19. Inflorescences racemes. Flowers with perianth; ovary multilocular or unilocular. 20
20. Leaf blades obtuse to rounded at base; petioles longer than leaf blades. Tepals papery (scarious). Fruits dehiscent.
 Amaranthaceae (Amaranthus)
20. Leaf blades acute at base; petioles shorter than leaf blades. Tepals not papery. Fruits indehiscent.
 Phytolaccaceae

Key to Keys | Key 1. Achlorophyllous Magnoliopsida | Key 2. Herbaceous Terrestrial or Aquatic Magnoliopsida | Key 3. Climbing Magnoliopsida | Key 4. Epiphytic Magnoliopsida | Key 5. Tree Magnoliopsida | Key 6. Shrub Magnoliopsida

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