Erythrostemon Klotzsch, in Link, Klotzsch & Otto, Icon. Pl. Rar. Horti. Berol. 2: 97, t. 39. 1844, descr. emended E. Gagnon & G. P. Lewis

Gagnon, Edeline, Bruneau, Anne, Hughes, Colin E., de Queiroz, Luciano Paganucci & Lewis, Gwilym P., 2016, A new generic system for the pantropical Caesalpinia group (Leguminosae), PhytoKeys 71, pp. 1-160 : 72-74

26 Erythrostemon Klotzsch, in Link, Klotzsch & Otto, Icon. Pl. Rar. Horti. Berol. 2: 97, t. 39. 1844, descr. emended E. Gagnon & G. P. Lewis Figs 41 , 42

Poincianella Britton & Rose (1930), pro parte, including the type species Caesalpinia mexicana A. Gray = Poincianella mexicana (A. Gray) Britton & Rose.

Schrammia Britton & Rose (1930).

Diagnosis.

Erythrostemon is closely related to Pomaria , but differs in habit, consisting of large shrubs and small to medium sized trees, or occasionally suffrutices (vs. shrubs, suffrutices, or perennial herbs in Pomaria ). It also differs by its ovate-lanceolate to orbicular sepals (vs. linear, laciniate sepals in Pomaria ), leaflets that are either eglandular or with conspicuous black sessile glands along the margin, these sometimes sunken in the sinuses of the crenulated margin (vs. leaflets with multiple glandular dots on the lower leaflet surfaces, that are orange in the field, drying black), the androecium and gynoecium free from the calyx (vs. the androecium and gynoecium cupped in the lower cucullate sepal), deflexed petals (vs. the two lower petals forming a horizontal platform above the lower cucullate sepal), and oblong-elliptic pods, the valves chartaceous to slightly woody, glabrous to pubescent, eglandular or with stipitate glands (vs. linear to sickle-shaped pods, the valves glabrous or with plumose trichomes and stipitate glands).

Type.

Erythrostemon gilliesii (Hook.) Klotzsch.

Emended description.

Shrubs or small to medium-sized trees varying from (0.5-) 1-12 (- 20) meters tall, occasionally suffrutices ( Erythrostemon nelsonii and Erythrostemon caudatus ), unarmed (except Erythrostemon glandulosus ); bark variable, smooth or rough, sometimes exfoliating, grey, greyish white, pale brown or reddish brown, often with white or black pustular lenticels; young stems terete (angular in Erythrostemon angulatus ), glabrous to densely pubescent, eglandular to densely covered in stipitate-glands. Stipules ovate-lanceolate, ovate to orbicular, apex acute to acuminate, caducous (persistent in Erythrostemon argentinus and Erythrostemon caudatus ). Leaves alternate, bipinnate, usually ending in a pair of pinnae plus a single terminal pinna; petioles (0.2-) 0.5-8 (- 10) cm long; rachis (0.5-) 1.2-14.5 (- 21.5) cm long, or lacking; petiole and rachis glabrous to densely pubescent, eglandular or covered in stipitate glands; pinnae in 1-6 (- 15) pairs, plus a terminal pinna (this occasionally lacking); leaflets in 2-13 (- 20) opposite pairs per pinna, size varying from a few mm in length and width (1.4-3 × 0.75-2 mm in Erythrostemon exilifolius ), to 5.3 × 2.5 cm, elliptic, oblong-elliptic, obovate, ovate or sub-orbicular, leaflet blades eglandular or with conspicuous black sessile glands along the margin, these sometimes sunken in the sinuses of the crenulated margin. Inflorescence an axillary or terminal raceme. Flowers bisexual, zygomorphic; calyx a short hypanthium with 5 sepals, 4.5-25 mm long, glabrous to pubescent, eglandular or with stipitate-glands, lower sepal cucullate in bud, all sepals caducous, the hypanthium persistent and abscising to form a free ring around the pedicel as the fruit matures; petals 5, free, imbricate, bright golden yellow, to creamish yellow, salmon pink or pink-scarlet, the median petal often with red-orange markings, the corolla diverse in form, the median petal 6-32 × 3.2-20 mm, the lateral petals 6-32 × 3.5-18.5 mm, petal blades eglandular or the dorsal surface covered with stipitate glands, claw margins glabrous to pubescent, eglandular or with gland-tipped trichomes; stamens 10, free, 0.6-3.5 cm long (up to 10 cm in Erythrostemon gilliesii ), filaments pubescent, eglandular or with stipitate glands; ovary pubescent, eglandular or with sessile or stipitate glands, stigma a terminal fringed chamber. Fruit a chartaceous to coriaceous or slightly woody, laterally compressed pod, with a marcescent style persisting as a small beak, elastically dehiscent with twisting valves, 2.4-12.5 × 1-2.8 cm, glabrous to pubescent, eglandular or with stipitate glands, (1-) 2-7 (- 8)-seeded. Seeds yellow to ochre-brown, or mottled with grey and black.

Geographic distribution.

The genus comprises 34 taxa in 31 species. Its circumscription is emended here to include many species previously placed in Central American and Mexican Poincianella . 22 species are found across the southern USA, Mexico and Central America, one occurs in the Caribbean (Cuba and Hispaniola), eight occur in South America, with one endemic in the caatinga vegetation of Brazil, and the other seven in Argentina, Bolivia, Chile, and Paraguay.

Habitat.

Low-elevation seasonally dry tropical forests across Mexico, Central America, the Caribbean and in caatinga vegetation in Brazil; also in patches of dry forest, deserts, yungas-puna transition zones, and chaco-transition forests in Argentina, Bolivia, Chile and Paraguay.

Etymology.

From erythro - (Greek: red) and stemon (Greek: stamen), the type species Erythrostemon gilliesii (Wall. ex Hook.) Klotzsch has long red exserted stamens, but this is unusual in the genus as circumscribed here.

Notes.

Species descriptions (under Caesalpinia binomials) are available in Lewis (1998). A key is also available in that revision, but it includes species now considered to belong in Cenostigma , Arquita , and Hoffmannseggia .

References.

Britton and Rose (1930); Burkart (1936: 82-84, 97-108); Ulibarri (1996); Lewis (1998); De Queiroz (2009: 120-121).

Figures

Figure 41. Erythrostemon gilliesii (Hook.) Klotzsch. A inflorescence and foliage B leaflet undersurface with submarginal glands C bract D detail of glandular pedicel E calyx opened out F median petal G upper lateral petal H lower lateral petal I stamen J gynoecium K stigma L fruit M seed. A from Venturi 5365 B, L from Kiesling et al. 4891 C-K from Cult. Kew 213 - 69 01878 M from Lewis 1417. Drawn by Eleanor Catherine.

Figure 42. Erythrostemon placidus (Brandegee) E. Gagnon & G. P. Lewis. A flowers (C. E. Hughes, Baja California, Mexico, Lewis 2031 (K )). Erythrostemon mexicanus (A. Gray) E. Gagnon & G. P. Lewis B inflorescence (C. E. Hughes, San Luis Potosi, Mexico, Hughes et al. 1606 (FHO )). Erythrostemon coccineus (G. P. Lewis & J. L. Contr.) E. Gagnon & G. P. Lewis C flowers (C. E. Hughes, Oaxaca, Mexico, Lewis et al. 1802 (K )). Erythrostemon pannosus (Brandegee) E. Gagnon & G. P. Lewis (captions continued on next page) D (G. P. Lewis, cultivated in University of Texas from seeds collected in Mexico, B. L. Turner 88 (TEX )). Erythrostemon exostemma (DC.) E. Gagnon & G. P. Lewis E flowers (G. P. Lewis, Comayagua, Honduras, Lewis & Hughes 1709 (K )). Erythrostemon gilliesii (Hook.) Klotzsch F Inflorescences (Stan Shebs, Wikicommons (https: // commons. wikimedia. org / wiki / File: Caesalpinia _ gilliesii _ 2. jpg), Nevada, U. S. A., unvouchered). Erythrostemon melanadenius (Rose) E. Gagnon & G. P. Lewis G inflorescence I fruit (C. E. Hughes, Oaxaca, Mexico, Hughes et al. 2091 (FHO )). Erythrostemon hintonii (Sandwith) E. Gagnon & G. P. Lewis H inflorescence J fruit (G. P. Lewis, Mexico, MacQueen et al. 428 (K )). Erythrostemon hughesii (G. P. Lewis) E. Gagnon & G. P. Lewis K unripe, ripe and dehisced fruits and seeds (C. E. Hughes, Oaxaca, Mexico, Lewis et al. 1795 (K )). Erythrostemon nicaraguensis (G. P. Lewis) E. Gagnon & G. P. Lewis L fruits (C. E. Hughes, Esteli, Nicaragua, Hawkins et al. 4 (FHO )). Erythrostemon exilifolius (Griseb.) E. Gagnon & G. P. Lewis M fruits (E. Gagnon, Argentina, Gagnon et al. 203 (MT )) Q flower and buds (E. Gagnon, Catamarca, Argentina, Gagnon & Atchison 222 (MT )). Eythrostemon fimbriatus (Tul.) E. Gagnon & G. P. Lewis N fruits (C. E. Hughes, La Paz Bolivia, Hughes et al. 2441 (FHO )). Erythrostemon cf. fimbriatus (Tul.) E. Gagnon & G. P. Lewis R flowers (C. E. Hughes, Santa Cruz, Bolivia, Hughes et al. 2466 (FHO )). Erythrostemon calycinus (Benth) L. P. Queiroz O flower (G. P. Lewis, Bahia, Brazil, unvouchered). Erythrostemon coulterioides (Griseb. emend. Burkart) E. Gagnon & G. P. Lewis P leaves, inflorescence with flowers and developing fruits (E. Gagnon, Jujuy, Argentina, Gagnon & Atchison 209 (MT).