Key to Species of Hamelia; by C.M. Taylor, based on Elias (1976)
1. Corolla infundibular or dilated, expanding gradually or abruptly toward the apex, yellow...Sect. Amphituba
2. Corolla tube 11-13 mm long, 3-5 mm wide at top; inflorescence a generally congested or compact dichasium, sometimes becoming lax in fruit; fruits 5-7 mm long; Central America and the Antilles to Bolivia.....Hamelia axillaris
2'. Corolla tube 18-50 m long, 4-20 mm wide at top; inflorescence a somewhat congested to lax dichasium or cyme; fruits 7-16 mm long; Mexico and the Greater Antilles to Ecuador.
3. Calyx lobes 3-5 mm long, elliptic-oblong to oblanceolate; stipules subulate; Central America and northwestern South America....Hamelia calycosa
3'. Calyx lobes 0.2-2.5 mm long, ovate, triangular, lanceolate, or elliptic-oblong; stipules tirangular to lanceolate.
4. Leaves, calyx, and corolla scabrous; Jamaica...Hamelia papillosa
4'. Leaves, calyx, and corolla glabrous to tomentose or villous; Mexico and the Antilles to Ecuador.
5. Calyx lobes apiculate; fruits 7-9 mm long; stipules 1-2 mm long; pedicels 4-9 mm long; Greater Antilles...Hamelia cuprea
5'. Calyx lobes acute but not apiculate; fruits 9-12 mm long; stipules 1.5-6 mm long; flowers sessile or with pedicels to 4 mm long; Mexico to Ecuador and Antilles.
6. Corolla tube flared or dilated gradually, 4-7 mm broad at top; inflorescence axes ascending, 8-26-flowered; Nicaragua to Colombia...Hamelia xerocarpa
6'. Corolla tubular at base then abruptly expanded, the tube 10-20 mm broad at top; inflorescence axes spreading to ascending, 4-14-flowered; Mexico to Ecuador and Antilles.
7. Corolla 23-31 mm long; leaves 7.5-27 x 4-14.2 cm, with 11-14 pairs of secondary veins; inflorescence mainly dichasial, 20-200-flowered; Costa Rica to Ecuador....Hamelia macrantha
7'. Corolla 31-50 mm long; leaves 4.5-14 x 1.7-4.6 cm, with 6-10 pairs of secondary veins; inflorescence scorpioid or helicoid, 6-24-flowered; Mexico, Jamaica.
8. Leaves glabrescent below; stipules triangular; corolla glabrous externally; fruit subcylidrical or lanceoloid; Jamaica...Hamelia ventricosa
8'. Leaves densely tomentose below; stipules 3-lobed, generally asymmetrically; corolla tomentose externally; fruit ellipsoid to subglobose; western Mexico....Hamelia xorullensis
1'. Corolla strictly tubular or cylindrical, not expanding toward apex, yellow, orange, or red....Sect. Hamelia
9. Inflorescence a reduced dichasium, borne on short lateral branchets, 3-5(-9)-flowered; leaves 1.5-8.7 x 0.8-4.8 cm, with 3-5 pairs of secondary veins; Panama.....H. sanguinea
9'. Inflorescence a dichasium. compound dichasium, cyme, or thyrse, terminal on main stems, 10-200-flowered; leaves 4.2-26 x 1.5-11 cm, with 3-11 pairs of secondary veins; Mexico, southern Florida, and the Antilles to Argentina.
10. Flowers and/or fruits not or weakly secund on inflorescence axes; stipules 1.5-2 mm long, subular to narrowly triangular; plants of Mexico and Jamaica.
11. Flowers pale to coppery yellow; peduncle 0.5-1 cm long; stipules subulate, persistent; leaves opposite; seeds 0.7-0.9 mm long; Jamaica....Hamelia chrysantha
11'. Flowers orange to red; peduncle 1.7-4.2 cm long; stipules narrowly triangular, caducous; leaves opposite or verticillate; seeds 1-1.2 mm long; Mexico....Hamelia versicolor
10'. Flowers and/or fruits not to markedly secund on inflorescence axes; stpules 2.2-7 mm long, linear to triangular; Mexico, southern Florida, and the Antilles to Argentina.
12. Inflorescence axes, calyx, and corolla densely hirtellous to villous; leaves sparsely to densely hirtellous to villous below.
13. Calyx lobes ovate, 0.5-1 mm long; leaves with secondary veins generally 7-10 pairs; seeds 0.6-0.9 mm long; common, Mexico, southern Florida, and the Antilles to Argentina....Hamelia patens
13'. Calyx lobes narrowly oblong to triangular, 1-4 mm long; leaves with secondary veins 3-5 pairs; seeds 1-1.2 mm long; occasional, Caribbean coast of southern Mexico and Central America to Panama....Hamelia rovirosae
12. Inflorescence axes, calyx, corolla, and leaves glabrous to puberulous, or more densely pubescent on costa and veins and/or with hirtellous domatia in abaxial axils of the secondary leaf veins.
14. Flowers all with well developed pedicels 6-12 mm long; petioles 4-6 cm long; southern Mexico to Nicaragua....Hamelia longipes
14'. Flowers sessile or with shorter pedicels, to 1.5 mm long; petioles 0.6-5.5 cm long; Mexico, southern Florida, and the Antilles to Argentina.
15. Inflorescence a compound, many-flowered dichasium; corolla yellow, tube 10-12 mm long, lobes 1.5-2 mm long; leaves with 11-16 pairs of secondary veins; seeds 0.4-0.5 mm long; Pacific coast of Costa Rica and western Panama.....Hamella magnifolia
15'. Inflorescence in several-flowered dichsia; corolla orange to red or occasionally yellow, tube 12-22 mm long, lobes 1.3-3.5 mm long; leaves with 6-10 pairs of secondary veins; seeds 0.5-0.9 mm long; Mexico, southern Florida, and the Antilles to Argentina.
16. Leaves with tufted-sericeous pubescence along costa on lower surface; pedicels 0.2-1.3 mm long; corollas yellow or yellow-tinged, with lobes 2.5-3.5 mm long; southern Mexico and Guatemala.....Hamelia barbata
16'. Leaves glabrous to puberulous below; flowers sessile or with pedicels to 1 mm long; corollas orange, red, or occasionally yellow, with lobes 1.3-2.5 mm long; Mexico, southern Florida, and the Antilles to Argentina....Hamelia patens