Paubrasilia E. Gagnon, H. C. Lima & G. P. Lewis, 2016

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 : 25-27

4. Paubrasilia E. Gagnon, H. C. Lima & G. P. Lewis gen. nov. Figs 8 , 9

Diagnosis.

Paubrasilia is closely related to Caesalpinia , but differs in habit, forming medium-sized to large trees, 5-15+ m tall, armed with small to large upturned prickles, these usually arising from woody protuberances (vs. shrubs or small to medium sized trees, usually 1-6 m tall, unarmed or armed with curved deflexed prickles, either occurring in pairs at the base of leaves, or scattered on shoots, or both, and sometimes present at the base of trunk). Paubrasilia also differs from Caesalpinia by having alternate pinnae with consistently alternate leaflets (vs. opposite pinnae with opposite to alternate leaflets), the median petal with a blood red central blotch (vs. the median petal lacking a red central blotch) and a spiny, woody, finely pubescent, sub-lunate, 1-2-seeded pod (vs. an unarmed, glabrous, oblong-elliptic, generally 3-7-seeded pod, with a marcescent style forming an acute apex).

Type.

Paubrasilia echinata (Lam.) E. Gagnon, H.C. Lima & G. P. Lewis ≡ Caesalpinia echinata Lam.

Description.

Medium sized to large trees, 5-15+ m tall, armed with small to large upturned prickles, these usually arising from woody protuberances, 1-20 mm long (the prickles often sparse or lacking on more mature specimens and larger, older branches); bark chestnut brown to almost black with greyish pustular lenticels, flaking in large woody plates; heartwood red, with the trunk exuding a red sap when injured. Stipules lanceloate, acute to acuminate, caducous. Leaves bipinnate, ending with a pair of pinnae; petiole and rachis finely tomentose; pinnae alternate, the terminal pair opposite to subopposite, with (2-) 3-20 pairs of pinnae per leaf; leaflets alternate, with (2-) 3-19 (-21) leaflets per pinna (generally the number of leaflets is inversely proportional to their size), 0.9-5 × 0.5-3.6 cm (although some specimens have leaflets up to 12 cm long), leaflet blades coriaceous, broadly oblong to subrhombic, apex rounded, obtuse or emarginate, base asymmetric, eglandular, glabrous, midvein excentric, secondary veins brochidodromous. Inflorescence a terminal, or occasionally axillary, finely tomentose raceme or panicle, with c. 15-40 flowers; bracts broadly ovate-triangular, apex acute to acuminate, less than 1 mm long, pubescent, caducous. Flowers bisexual, zygomorphic; calyx a tomentose hypanthium with 5 sepals, that are c. 5-9 mm long, the lowest sepal cucullate, covering the other 4 in bud, all sepals caducous but the hypanthium persisting as a free ring around the pedicel as the pod matures; petals 5, free, bright yellow, the median petal with a blood-red blotch on the inner face, c. 11-15 × 4-10 mm, all petals eglandular, broadly-obovate to slightly spathulate, the petal claws pubescent; stamens 10, free, 7-9 mm long, eglandular, densely pubescent on lower half; ovary pubescent with small spines intermixed, stigma a subterminal fringed-chamber. Fruit a spiny, finely pubescent, sub-lunate, woody, 5.5-7.3 × 1.9-2.6 cm, elastically dehiscent pod with twisting valves, 1-2-seeded. Seeds laterally compressed, ovate-obovate.

Geographic distribution.

A monospecific genus endemic to Eastern Brazil, in the states of Pernambuco, Bahia, Espirito Santo and Rio de Janeiro. Widely cultivated in Brazil as an ornamental street or park tree, and sometimes in plantations.

Habitat.

Dry coastal cactus scrub often on rocky outcrops, inland in Mata Atlântica, and in tall restinga on well-drained sandy soil.

Etymology.

“Pau-brasil” is the national tree of Brazil, and has long been associated with the country. Its red sap was once used for dying cotton and cloth and its wood is much prized for the manufacture of high quality violin bows. Originally described as Caesalpinia echinata by Lamarck in 1785, it is appropriate that this phylogenetically isolated taxon should be placed in its own monospecific genus and a Latinization of its well-known and much used common name recognises the importance of the species to Brazil. For a detailed account of this iconic species refer to Pau-brasil by E. Bueno [et al.], São Paulo, Axis Mundi (2002).

References.

Lewis (1998: 152-158); Bueno (2002); Cardoso et al. (2005).

Figures

Figure 8. Paubrasilia echinata (Lam.) E. Gagnon, H. C. Lima & G. P. Lewis. A inflorescences and foliage B leaflet undersurface C bark armature (front and side views) D flower E flower l. s. F median petal G upper lateral petal H lower lateral petal I stamen J gynoecium K stigma L fruit M single valve of dehisced fruit N seedling. A from Glaziou 6839 B, K from Angeli 201 C, M from Lewis et al. 1634 D from Lima et al. 2705 E-J from Ducke 20623 L from Mell s. n., N from Lewis et al. 1624. Drawn by Tim Galloway.

Figure 9. Paubrasilia echinata (Lam.) E. Gagnon, H. C. Lima & G. P. Lewis. A flowers (H. C. Lima, Brazil, Lima et al. 2705 (RB )) B fruits (G. P. Lewis, Brazil, unvouchered) C prickles on woody protuberances on a young trunk (E. Gagnon, Bahia, Brazil, Lima et al. 7909 (RB )) D habit (L. P. de Queiroz, Bahia, Brazil, unvouchered) E fluted trunk of a mature individual (E. Gagnon, Bahia, Brazil, Lima et al. 7894 (RB) F cross section of the trunk, showing dark red heartwood (E. Gagnon, Espirito Santo, Brazil, unvouchered), G inflorescences (L. P. de Queiroz, Bahia, Brazil, unvouchered).