Cenostigma Tul., Ann. Sci. Nat., Bot., ser . 2. 20: 140. 1843, 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 : 54-55

18. Cenostigma Tul., Ann. Sci. Nat., Bot., ser. 2. 20: 140. 1843, descr. emended E. Gagnon & G. P. Lewis Figs 29 , 30

Poincianella Britton & Rose. 1930, pro parte, excluding the type.

Diagnosis.

Cenostigma is morphologically most similar to the genus Erythrostemon . It differs from the latter by its leaves with alternate to subopposite (occasionally opposite) leaflets (vs. leaflets consistently opposite in Erythrostemon ). A number of other characters can help to distinguish between the two genera, but these are not constant across species of Cenostigma . For example, a stellate indumentum on the leaflets, inflorescences, and/or sepals is found on some, but not all Cenostigma species, but is always lacking in Erythrostemon . Black subepidermal glands (visible with a × 20 lens) can be found scattered in the undersurface of leaflets and/or on sepals in Cenostigma (vs. these always lacking in Erythrostemon ). Cenostigma pods are generally woody with thickened margins or an adaxial, proximal woody ridge or crest (vs. less robust pods lacking any woody ridge or crest in Erythrostemon ).

Type.

Cenostigma macrophyllum Tul.

Emended description.

Unarmed multi-stemmed shrubs, small compact trees, (0.3-) 0.5-6 m, or large trees to 35 m tall, the larger trees with fluted trunks at maturity ( Cenostigma bracteosum , Cenostigma pluviosum , Cenostigma eriostachys , Cenostigma tocantinum and Cenostigma macrophyllum ); bark smooth, or occasionally rough and flaking (some infraspecific taxa of Cenostigma pluviosum ), brown, grey, or mottled silver or grey; young shoots terete, glabrous to pubescent, glandular to eglandular. Stipules red, with ciliate margins, broadly ovate with a rounded apex, and caducous in Cenostigma pyramidale , not seen in other species. Leaves alternate, pinnate or bipinnate and then ending in a pair of pinnae plus a single terminal pinna, glabrous to densely pubescent, sometimes with stellate hairs or various types of sessile or stalked glands; petioles (0.1-) 0.6-4.8 (-6) cm, rachis 0.5-17 (- 26.5) cm; species with pinnate leaves ( Cenostigma tocantinum , Cenostigma marginatum , Cenostigma pinnatum , and Cenostigma macrophyllum ) either with three leaflets or 2-9 pairs of opposite leaflets; species with bipinnate leaves with 1-11 pairs of opposite to alternate pinnae, plus a terminal pinna, each pinna with 3-29 alternate to subopposite (occasionally opposite) individual leaflets; leaflets vary greatly in size, 0.5-15 × 0.1-7 cm, glossy on the upper surface, usually more or less coriaceous (chartaceous in Cenostigma tocantinum ), ovate-elliptic, lanceolate with an acute to acuminate apex (some specimens of Cenostigma tocantinum ), obovate, oblong-elliptic or suborbicular, apex rounded or emarginate, mucronate, base cuneate, cordate or truncate, the blade often inequilateral at the base, eglandular, or with black subepidermal glands (visible with a × 20 lens) scattered on the undersurface, and/or with conspicuous, sessile or punctate glands on the undersurface or along the margins, in addition to stipitate glands; veins usually prominent, main vein often excentric, secondary venation brochidodromous. Inflorescences either axillary or terminal racemes, these sometimes pyramidal in shape, sometimes aggregated into large showy panicles, inflorescence rachis and pedicels densely tomentose to glabrescent, sometimes covered in stellate hairs, these occasionally intermixed with stipitate glands; pedicels 5-22 mm long, articulated; bracts 2.5-6 mm long, caducous. Flowers bisexual, zygomorphic; calyx a short hypanthium with 5 sepals, 4.5-9 (- 11) mm long, the lower cucullate sepal generally slightly longer than the other four, apices entire or with a fimbriate-glandular margin, puberulous or tomentose, sometimes with a dense stellate indumentum ( Cenostigma eriostachys , Cenostigma tocantinum and Cenostigma macrophyllum ), the sepal lobes eglandular or with scattered dark, subepidermal glands, caducous, but the hypanthium persisting as a calyx ring in fruit; all 5 petals free and clawed, bright yellow, the median petal (7.5-) 9-15 (- 19) × 5-13 (- 17) mm, with red or orange markings on the inner surface of the blade, suborbicular to elliptic or spathulate, with a thickened, pubescent claw, the outer surface of which has short-stalked glands, these sometimes also on the dorsal surface of the blade, lateral petals 0.9-2.7 × 0.4-2 cm, broadly elliptic, sub-rectangular, obovate or suborbicular, petal claws pubescent and with stalked-glands, these sometimes also on the dorsal surface of the blade; stamens 10, free, filaments (7-) 8-14 (-21) mm long, pubescent on lower ⅔ to ½, with short-stipitate glands along entire length (except in Cenostigma macrophyllum ); ovary pubescent with glands intermixed, these sometimes obscured by the indumentum, stigma a terminal fringed-chamber. Fruits laterally compressed, coriaceous to woody pods, (3.8-) 5-14 (- 16) × 1.2-3.3 (- 3.7) cm, with conspicuously thickened margins (an adaxial, proximal woody ridge or crest in Cenostigma macrophyllum ), elastically dehiscent (sometimes tardily), the valves twisting at maturity, either glabrous or pubescent, smooth or prominently reticulately veined (on herbarium specimens), usually eglandular or with a few scattered stipitate or sessile glands (densely glandular in Cenostigma microphyllum ). Seeds 2-6 (- 8) per pod, ovate-elliptic to ovate-orbicular, 9-19 × (6-) 8-12 × 1-3 mm, ochre, brown, or mottled, shiny.

Geographic distribution.

We recognise 20 taxa in 14 species, all of them neotropical; only two of these taxa do not require new names, while the rest are species of Caesalpinia here transferred to Cenostigma . The majority of species are found in central and NE Brazil, including parts of the Amazon. Two species extend around the circum-Amazonian arc of dry forests and adjacent cerrado, including in Paraguay, Argentina and Bolivia, and one taxon is also found in the seasonally dry inter-Andean valleys of Peru. Species are also found throughout Central America, from Panama northwards and in Mexico, extending to the Caribbean, with endemics in Cuba and Hispaniola.

Habitat.

Seasonally dry tropical forest, bushland and thicket (restinga, caatinga, semi-arid thorn scrub), wooded grassland (cerrado and cerradão) and terra firme forest.

Etymology.

From ceno - (Greek: empty) and stigma, presumably alluding to the chambered stigma (a character of many species of the Caesalpinia Group, and not restricted to Cenostigma ).

References.

Lewis (1987: 34-35, 1998); Freire (1994); Ulibarri (1996); De Queiroz (2009: 129-130, see also under Poincianella , 121-128); Warwick and Lewis (2009); Lewis et al. (2010).

Figures

Figure 29. Cenostigma eriostachys (Benth.) E. Gagnon & G. P. Lewis. A part of bipinnate leaf B median leaflet undersurface, C section of branchlet bark D inflorescence E flower F calyx opened out G detail of stellate hairs on calyx H median petal I median petal claw J upper lateral petal K detail of lateral petal claw L stamen M gynoecium N stigma O fruit P seed Q seedling R bruchid emerged from seed. A, B, P-R from Lewis & Hughes 1799 C from Lewis et al. 1719 D-N from Lewis et al. 1718 O from Lewis & Hughes 1775. Drawn by Sue Wickison.

Figure 30. Cenostigma macrophyllum Tul. A flower (G. P. Lewis, Piaui, Brazil, Lewis 1342 (K )) B fruit (G. P. Lewis, Brazil, unvouchered). Cenostigma eriostachys (Benth.) E. Gagnon & G. P. Lewis C fruits (C. E. Hughes, Oaxaca, Mexico, Hughes 1935 (FHO )) I flowers (G. P. Lewis, Mexico, MacQueen et al. 408 (K )). Cenostigma pluviosum (DC.) E. Gagnon & G. P. Lewis cf. var. intermedium (G. P. Lewis) E. Gagnon & G. P. Lewis D fruit F inflorescence H a new flush of leaves (E. Gagnon, Bahia, Brazil, H. C. Lima et al. 7901 (RB )). Cenostigma pluviosum var. cabralianum (G. P. Lewis) E. Gagnon & G. P. Lewis E fruits (G. P. Lewis, Brazil, Lewis et al. 2019 (K )). Cenostigma marginatum (Tul.) E. Gagnon & G. P. Lewis G leaves and fruits (C. E. Hughes, Bolivia, Wood et al. 26514 (K )). Cenostigma pluviosum (DC.) E. Gagnon & G. P. Lewis var. pluviosum J inflorescences L inflorescences, foliage and dehisced fruits (C. E. Hughes, Santa Cruz, Bolivia, Wood et al. 26552 (K )). Cenostigma gaumeri (Greenm.) E. Gagnon & G. P. Lewis K inflorescence (C. E. Hughes, Quintana Roo, Mexico, Lewis & Hughes 1762 (K )).