Xylia Benth., J. Bot. (Hooker) 4: 417. 1842.

Bruneau, Anne, de Queiroz, Luciano Paganucci, Ringelberg, Jens J., Borges, Leonardo M., Bortoluzzi, Roseli Lopes da Costa, Brown, Gillian K., Cardoso, Domingos B. O. S., Clark, Ruth P., Conceicao, Adilva de Souza, Cota, Matheus Martins Teixeira, Demeulenaere, Else, de Stefano, Rodrigo Duno, Ebinger, John E., Ferm, Julia, Fonseca-Cortes, Andres, Gagnon, Edeline, Grether, Rosaura, Guerra, Ethiene, Haston, Elspeth, Herendeen, Patrick S., Hernandez, Hector M., Hopkins, Helen C. F., Huamantupa-Chuquimaco, Isau, Hughes, Colin E., Ickert-Bond, Stefanie M., Iganci, Joao, Koenen, Erik J. M., Lewis, Gwilym P., de Lima, Haroldo Cavalcante, de Lima, Alexandre Gibau, Luckow, Melissa, Marazzi, Brigitte, Maslin, Bruce R., Morales, Matias, Morim, Marli Pires, Murphy, Daniel J., O'Donnell, Shawn A., Oliveira, Filipe Gomes, Oliveira, Ana Carla da Silva, Rando, Juliana Gastaldello, Ribeiro, Petala Gomes, Ribeiro, Carolina Lima, Santos, Felipe da Silva, Seigler, David S., da Silva, Guilherme Sousa, Simon, Marcelo F., Soares, Marcos Vinicius Batista & Terra, Vanessa, 2024, Advances in Legume Systematics 14. Classification of Caesalpinioideae. Part 2: Higher-level classification, PhytoKeys 240, pp. 1-552 : 1

Xylia Benth., J. Bot. (Hooker) 4: 417. 1842.

Figs 104 , 105 , 106 , 112

Esclerona Raf., Sylva Tellur.: 120. 1838. Type: Esclerona montana Raf. [= Xylia xylocarpa (Roxb.) Taub. (≡ Mimosa xylocarpa Roxb.)]

Xylolobus Kuntze, Lex. Gen. Phan.: 598. 1903, nom. superfl. Type not designated.

Type.

Xylia dolabriformis Benth. [= Xylia xylocarpa (Roxb.) Taub. var. xylocarpa (≡ Mimosa xylocarpa Roxb.)]

Description.

Shrubs or trees, (6) 15-30 m tall, to 40 cm diameter, unarmed, evergreen or deciduous (Fig. 104B ); golden pubescent on the calyx, corolla, and young stems; bark dark red brown to grey, rough or scaly (Fig. 104A ); brachyblasts absent. Stipules lanceolate-linear, to 1 cm, precocious on new growth, sessile, caducous. Leaves large, bipinnate, nectary borne at the apex of the rachis between the pinnae, round, mound-shaped, nectaries usually also variably borne between distal pairs of leaflets, and sometimes between all pairs of leaflets; pinna 1 pair, 5-30 cm long; leaflets 3-20 pairs per pinna, opposite, the proximal pair sometimes reduced to a single leaflet, petiolulate, oblanceolate to lanceolate. Inflorescences of capitula or congested umbels (Fig. 105D ) on longish, usually flattened (exception X. hoffmannii (Vatke) Drake) peduncles, 1-2 per axil, borne in the axils of coeval leaves or more often aggregated into paniculiform secondary inflorescences on older branches from which the leaves have abscised, flower-bearing branches apparently indeterminate. Flowers sessile or appearing pedicellate in some species by elongation of the receptacle, floral bracts peltate and pedicellate, pubescent; calyx connate, 5-lobed, valvate or slightly imbricate in bud; petals 5, free or connate, pale yellow to cream or dark red, valvate in bud; stamens 10, the filaments sometimes flattened and ribbon-like, anthers dorsifixed, usually bearing a caducous, stalked anther gland; pollen in calymmate 8, 12, or 16- grained polyads; ovary sessile, densely pilose, the style attached to one side of the ovary, style exserted, stigma porate. Fruit a woody legume, explosively dehiscent from the apex through both sutures, dolabriform (Fig. 106D ), 5-15 × 5-6 cm, ca. 4-10-seeded, the valves recurved after dehiscence, the exocarp dull, cracking and falling away to expose a longitudinally veined, fibrous mesocarp, interior of fruit smooth. Seeds obliquely or transversely inserted, sunken into indentations in the pod, brown, funicles fleshy and enlarged, testa hard, pleurogram present.

Included species and geographic distribution.

Nine species, West Africa from Guinea to Ghana; central and southern Africa from Democratic Republic of the Congo to Tanzania, Mozambique, and South Africa, Madagascar, India, and South East Asia (Fig. 112 ).

Chromosome number.

n = 12 ( Moore 1974, 1977; Goldblatt 1981b).

Ecology.

Evergreen, semi-deciduous and gallery forests.

Etymology.

From the Greek xylon, referring to the very hard wood in this genus.

Human uses.

Valued as a timber tree. The wood is very hard and is used in heavy construction, for houses, bridges, ship building, and tools as well as for fuel and charcoal. Used in reforestation in South East Asia. Seeds are eaten as a vegetable, and the bark and seeds are used in folk medicine to treat a wide variety of ailments. Xylia xylocarpa is grown as a shade tree in India ( Fern 2023).

Notes.

Xylia has distinctive woody, dolabriform legumes, seen elsewhere only in Pentaclethra , Calypocalyx , Pseudoprosopis and Dimorphandra . The inflorescences vary from 1-2 heads borne in the axils of coeval, well-developed leaves in some species to complex paniculiform inflorescences with numerous aggregated heads and suppressed leaves in other species. In a few species, simple, linear bracts are present in the inflorescence instead of leaves and the peduncles may bear 1-several bracts below the developing inflorescences. Generally, these bracts are caducous. Inflorescences are also characterised by having precocious development of the foliar glands which reach their full size on very small leaves. The glands are conspicuous in the inflorescence and possibly serve either to distract potential floral predators from the developing flowers or to attract protectors. Likewise, the terminus of the rachis is precociously developed, overtopping the pinnae and leaflets, and appearing bract-like. As discussed in more detail in the Adenanthera clade notes, Calpocalyx is nested within Xylia , rendering the latter non-monophyletic (Fig. 103 ).

Taxonomic references.

Brenan (1959); Villiers (2002).

Figures

Figure 103. Generic relationships in the Adenanthera clade (tribe Mimoseae). For description of phylogeny and support values, see Fig. 6 caption (page 63).

Figure 104. Habit and growth form in the Adenanthera clade A Xylia xylocarpa var. kerrii (Craib & Hutch.) I. C. Nielsen scaly bark B Xylia torreana Brenan canopy C Pentaclethra macroloba (Willd.) Kuntze trunk showing buttresses D Tetrapleura tetraptera (Schumach. & Thonn.) Taub. canopy (Harris 9659) E Amblygonocarpus andongensis (Welw. ex Oliv.) Exell & Torre pale grey, scaly bark (Catarino 2067) F Pseudoprosopis gilletii (De Wild.) Villiers liana with leaves and lignified tendrils (Texier 1558) G Adenanthera pavonina L. thin scaly bark H habit I Amblygonocarpus andongensis (Welw. ex Oliv.) Exell & Torre growing in savanna (Coates Palgrave M 806). Photo credits A Dechaphaetkrathok B F du Randt C D DeMelo D DJ Harris E L Catarino F N Texier G, H Shelbyfarmer I M Coates Palgrave.

Figure 105. Flowers and inflorescences in the Adenanthera clade A Adenanthera pavonina L. inflorescence B, C Tetrapleura tetraptera (Schumach. & Thonn.) Taub. (Harris 9663) B reflexed petals and white filaments on the flowers C racemose inflorescence D Xylia hoffmannii (Vatke) Drake umbellate inflorescence (Ratovoson 838) E Calpocalyx klainei Pierre ex Harms inflorescence (Texia 976) F Pseudoprosopis bampsiana Lisowski flower detail showing pseudopedicels (Bidault 2515) G, H Pentaclethra macroloba (Willd.) Kuntze G inflorescences congested at the ends of branches H close-up of the inflorescence showing the long filamentous staminodes. Photo credits A CheongWeei Gan B, C DJ Harris D F Ratovoson E N Texia F E Bidault G, H D Cardoso.

Figure 106. Fruits and seeds in the Adenanthera clade A Adenanthera pavonina L. dehisced fruits with exposed persistent red seeds B Amblygonocarpus andongensis (Welw. ex Oliv.) Exell & Torre Indehiscent four-angled fruits (Catarino 2067) C Pseudoprosopis fischeri Harms young fruit (Bingham 8055) D Xylia xylocarpa var. kerrii (Craib & Hutch.) I. C. Nielsen young dolabriform pod E Tetrapleura tetraptera (Schumach. & Thonn.) Taub. immature winged, indehiscent pod (Harris 9659) F Pentaclethra macrophylla Benth. pod and recalcitrant seeds G, H Calpocalyx ngouniensis Pellegr. woody valves from dehisced pod (Texier 695). Photo credits A Shelbyfarmer B L Catarino C MG Bingham D B Peroth E DJ Harris 9659 F CJ Porto, Fundacion Tierra Iberica G H N Texier.

Figure 112. Distribution of Xylia based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.