Erythrostemon Klotzsch in Link, Klotzsch & Otto, Icon. Pl. Rar. Horti. Berol. 2: 97, t. 39. 1844.

Figs 35, 36, 38, 47

Poincianella Britton & Rose, N. Amer. Fl. 23(5): 327. 1930. Type: Poincianella mexicana (A. Gray) Britton & Rose [≡ Caesalpinia mexicana A. Gray (≡ Erythrostemon mexicanus (Rose) Gagnon & G.P. Lewis)]

Schrammia Britton & Rose, N. Amer. Fl. 23(5): 317. 1930. Type: Schrammia caudata (A. Gray) Britton & Rose [≡ Hoffmannseggia caudata A. Gray (≡ Erythrostemon caudatus (A. Gray) Gagnon & G.P. Lewis)]

Type.

Erythrostemon gilliesii (Hook.) Klotzsch [≡ Poinciana gilliesii Hook.]

Description.

Shrubs or small to medium-sized trees, occasionally suffrutices, unarmed (except E. glandulosus (Bertero ex DC.) Gagnon & G.P. Lewis). Stipules ovate-lanceolate, ovate, or orbicular, acute to acuminate, sometimes foliaceous, cordate and auriculate at the base, caducous or less often persistent. Leaves bipinnate, usually ending in a single terminal pinna; pinnae in 1-6 (15), opposite pairs; leaflets in 2-13 (20) opposite pairs per pinna, 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; hypanthium persistent as a wide or narrow, shallow or deep cup, or sometimes abscising to form a free ring around the pedicel apex as the fruit matures; sepals 5, lower sepal cucullate in bud, all sepals caducous; petals 5, free, bright golden yellow to creamish yellow, salmon pink or pink-scarlet, the median petal often with red-orange markings, the corolla diverse in form; stamens 10, free, filaments pubescent, eglandular or with stipitate glands; ovary pubescent, eglandular or with sessile or stipitate glands. Fruit a chartaceous to coriaceous or slightly woody, laterally compressed legume, elastically dehiscent with twisting valves, eglandular or with stipitate glands, (1) 2-7 (8)-seeded. Seeds yellow to ochre-brown or mottled with grey and black.

Chromosome number.

2 n = 24 [ E. exostemma (Moc. & Sessé ex DC.) Gagnon & G.P. Lewis, E. gilliesii, E. hughesii (G.P. Lewis) Gagnon & G.P. Lewis, E. melanadenius (Rose) Gagnon & G.P. Lewis, E. mexicanus (Rose) Gagnon & G.P. Lewis, E. nelsonii (Britton & Rose) Gagnon & G.P. Lewis, E. yucatanensis (Greenm.) Gagnon & G.P. Lewis] (Fedorov 1969; Cangiano and Bernardello 2005; Mata-Sucre et al. 2020).

Included species and geographic distribution.

Thirty-four taxa in 31 species: 22 species are found across the southern USA, Mexico, and Central America, one occurs in the Caribbean (Cuba and Hispaniola), and eight occur in South America (Fig. 47).

Ecology.

Seasonally dry tropical forests across the Neotropics; also occurring in deserts, yungas-puna transition zones, and chaco-transition forests (Argentina, Bolivia, Chile, Paraguay).

Etymology.

From Greek, erythro - (= red) and stemon (= stamen), the type species E. gilliesii has long red exserted stamens, but this is unusual in the genus as circumscribed here.

Human uses.

Erythrostemon gilliesii is widely cultivated as a garden ornamental and is hardy in Mediterranean and temperate regions (Lewis 2005b).

Notes.

Originally described as a monospecific genus, its circumscription was recently emended to include many species previously placed in Central American and Mexican Poincianella (Gagnon et al. 2016).

Taxonomic references.

Britton and Rose (1930); Burkart (1936); Gagnon et al. (2016); Lewis (1998, 2005b); Queiroz (2009); Ulibarri (1996).