Key to Neotropical Species of Margaritopsis
1. Leaves ovate to lanceolate, subsessile, mucronate or with a spine at the apex; flowers 1 to 3; Cuba, Hispaniola.
2. Peduncles to 6 mm long.... M. lanceifolia
2. Peduncles 1-2 mm long.
3. Flowers solitary; corollas 1-2 mm long; Cuba... M. acuifolia
3. Flowers 3; corollas ca. 3.5 mm long; Hispaniola....M. triflora
1. Leaves elliptic to lanceolate, oblanceolate, elliptic-oblong, narrowly elliptic, lanceolate, or obovate, petiolate to subsessile, at apex entire; flowers 1--numerous; throughout the Neotropics.
4. Inflorescences capitate to subcapitate.
5. Calyx limbs 2-5 mm long, truncate to shallowly lobed with lobes obtuse to rounded.
6. Stipules united in a subtruncate to truncate sheath; fruits ca. 5 mm long...M. deinocalyx
6. Stipules triangular to ligulate on each interpetiolar side; fruits 10-25 mm long.
7. Fruits 17-25 mm long.... M. paupertina
7. Fruits 10-12 mm long.... M. podocephala
5. Calyx limbs 0.2-3.5 mm long or shorter, truncate or denticulate to deeply lobed, if 2 mm long or longer then lobed for 1/3 or more with the lobes acute.
8. Inflorescences sessile, involucrate with the external bracts small but clearly larger than the other bracts and enclosing them and the flowers.
9. Involucral bracts several, obtuse to truncate; leaves 5-14 x 1.5-5 cm; Central America to northern South America...M. kappleri
9. Involucral bracts 2, acute; leaves 1-5.5 x 0.5-3 cm; southeastern Brazil...M. schuechiana
8. Inflorescences sessile to pedunculate, ebracteate or bracteate but bracts not involucral, if external bracts surround part of inflorescence then these similar to the other bracts.
10. Stipules truncate, denticulate, or bilobed but with lobes less than 1 mm long and persistent.
11. Inflorescences with well developed peduncles 5-25 mm long....M. chaenotricha
11. Inflorescences sessile or subsessile with peduncles to 3 mm long.
12. Flowers 1-2; leaves 0.8-2 mm wide....M. carrascoana
12. Flowers 5 to numerous; leaves 10-70 mm wide.
13. Corolla tubes 3 mm long, corolla lobes with terminal appendages ca. 0.2 mm long; widespread in Amazon basin to eastern Brazil and Paraguay....M. cephalantha
13. Corolla tubes 2-2.5 mm long, corolla lobes with terminal appendages 0.3--0.5 mm long; Amazon basin and Guayana Highlands....M. pallidinervia
10. Stipules with 1 to several lobes 1-3 mm long, persistent or sometimes caducous.
14. Calyx lobes 1-3.5 mm long, usually spreading to reflexed; Central America to northwestern Ecuador....M. haematocarpa
14. Calyx lobes 1 mm long or less, usually ascending; South America.
15. Inflorescences capitate, in shape subglobose; Guianas...M. guianensis
15. Inflorescences capitate to subcapitate, in shape regularly to irregularly subglobose to patelliforme; Central America through southern South America.
16. Calyx limb lobed for 1/3-1/2 of its length; inflorescences capitate; Surinam and northeastern Brazil.... M. wilhelmensis
16. Calyx limb lobed shallowly or for up to 1/4 of its length; inflorescences subcapitate to congested cymose.
17. Leaves oblanceolate; peduncles 1-5 mm long; western Amazon basin....M. nana
17. Leaves elliptic to elliptic-oblong; peduncles 5-15 mm long; Amazon basin to eastern Brazil and Paraguay.
18. Corolla tube 1-1.5 mm long; leaves 4-11 x 1-5 cm; Amazon basin to eastern Brazil and Paraguay...M. chaenotricha
18. Corolla tube 4-5 mm long; leaves 1.5-7.5 x 0.5-2.5 cm; Paraguay...M. hassleriana
4. Inflorescences branched with secondary axes developed.
19. Stipule lobes 0.5-3.5 mm long, persistent or caducous, if less than 1 mm long then caducous.
20. Calyx limbs 0.5-0.6 mm long....M. albert-smithii
20. Calyx limbs 1-4 mm long (including lobes).
21. Leaves oblanceolate, shortly rounded to obtuse at base....M. huallagae
21. Leaves elliptic to elliptic-oblong, acute to cuneate at base.
22. Calyx limb lobed for 1/3-1/2 of its length, lobes narrowly triangular to linear, acute; fruits 5-6 x 5-6 mm....M. haematocarpa
22. Calyx limb lobed shallowly, for 1/4 of its length or less, lobes triangular, obtuse to rounded; fruits 17-25 x 15-17 mm....M. paupertina
19. Stipule lobes less than 1.5 mm long and persistent.
23. Leaves abaxially with pilosulous patches in the axils of the secondary veins; plants of dry and seasonal forests.
24. Leaves narrowly elliptic to oblanceolate with the secondary veins prominent abaxially; calyx limbs 1-1.5 mm long; Cuba and Hispaniola....M. agustinae
24. Leaves oblanceolate to obovate or elliptic-oblong with the secondary veins plane to prominulous abaxially; calyx limbs 1.2-2 mm long; throughout the Antilles and in Mexico, Central America and northern South America.
25. Inflorescences 5- to several flowered; throughout the Antilles and in Mexico, Central America and northern South America....M. microdon
25. Inflorescences 2-3-flowered; Cuba and Hispaniola....M. nutans
23. Leaves abaxially without pilosulous patches in the axils of the secondary veins; plants of seasonal to moist and wet forests.
26. Inflorescences pyramidal, with the primary axis longer and more branched than the secondary axes.
27. At least some flowers sessile....M. boliviana
27. Flowers all pedicellate....M. cymuligera
26. Inflorescences corymbiform, with the secondary axes as well as or better developed than the primary axis.
28. Pyrenes unridged or with shallow, rounded to acute, longitudinal ridges separated by a smooth to finely rugulose surface.
29. Flowers pedicellate; Nicaragua to northeastern Colombia...M. impatiens
29. Flowers sessile; southeastern Brazil and Paraguay...M. chaenotricha
28. Pyrenes with well developed, rounded, longitudinal ridges and the surface otherwise smooth; northern South America.
30. Inflorescences with branched portion 1-3.5 x 1.5-4 cm, the primary axis well developed...M. astrellantha
30. Inflorescences with branched portion 0.5-1 x 1.2-3.5 cm, the primary axis shorter than the secondary axes....M. inconspicua