Pachyelasma Harms, Bot. Jahrb. Syst. 49: 428. 1913.

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

Pachyelasma Harms, Bot. Jahrb. Syst. 49: 428. 1913.

Figs 99 , 101 , 102

Type.

Pachyelasma tessmannii (Harms) Harms [≡ Stachyothyrsus tessmannii Harms]

Description.

Unarmed trees, frequently emergent above forest canopies, to 60 m and 2.5 m diameter (Fig. 99C ), frequently buttressed; bark greyish and rugose, thick, peeling off in irregular flakes; short shoots absent. Stipules inconspicuous, caducous. Leaves bipinnate, petiole and leaf rachis cylindrical; pinnae 2-3 pairs, opposite or, rarely, subopposite, articulated with leaf rachis; leaflets 9-14 per pinna, alternate, oblong or oblong-lanceolate, coriaceous, pinnately veined, shortly petiolulate; stipels not seen; extrafloral nectaries absent. Inflorescences densely flowered spicate racemes, clustered in short axillary panicles, the peduncle short or absent and a short rachis. Flowers small (ca. 5 mm long), wine red with a yellowish base, actinomorphic, bisexual or unisexual (staminate), pedicellate; hypanthium short, cupuliform; sepals 5, free; petals 5, free, imbricate, obovate, margins ciliate; stamens 10, free, equally long, anthers dehiscing through longitudinal slits, dorsally attached to a massive connective; pollen in isopolar, trizonocolporate monads, exine perforate to finely rugulate; intrastaminal disk attached to the hypanthium surface; ovary shortly stipitate, glabrous, ovules numerous (15-20), style cylindrical, stigma punctiform. Fruit indehiscent or late dehiscent, with a thick body, flat compressed, straight or slightly curved, oblong or oblong-lanceolate, each margin provided with two thick erect ribs; valves thick, smooth, the mesocarp gelatinous-resinous, the endocarp internally septate into 10-15 one-seeded envelopes. Seeds ellipsoid, only slightly compressed, testa bright, pleurogram absent.

Chromosome number.

Unknown.

Included species and geographic distribution.

Monospecific ( P. tessmannii ), distributed in west tropical Africa (Nigeria, Cameroon, Central African Republic, Equatorial Guinea, Gabon, Congo, Democratic Republic of Congo; Fig. 102 ).

Ecology.

Tropical lowlands rainforests of the Guinean and Congolian ecoregions.

Etymology.

From the Greek, pachy - (= thick) and elasmos (= plate), in reference to the thick pod.

Human uses.

Pachyelasma tessmannii , locally known as Mekogho and Mundumbula in Gabon, is used medicinally in various capacities. Fruits are used in traditional folk medicine to cure diarrhoea and abdominal pain ( Betti 2002). The root bark exhibits potent molluscicidal properties against the schistosomiasis snail Biomphalaria glabrata (Say, 1818) ( Nihei et al. 2005). Crushed pods and bark are used as an abortifacient and fish poison (Mouele 2022).

Notes.

Pachyelasma tessmannii is a dominant tree in West African rainforests, where it is one of the tallest trees, frequently emergent beyond the forest canopy. Its flowers are described as having a very unpleasant odour at night, which can be detected even from a distance of 300 m (Breteler 1026, P).

Taxonomic references.

Harms (1913) with illustration.

Figures

Figure 99. Habit, bark and foliage of Erythrophleeae A Erythrophleum fordii Oliv. at Hung Temple, Vietnam B bark of Erythrophleum couminga Baill. in Madagascar C Pachyelasma tessmannii (Harms) Harms in Congolian rainforest D, E, H Erythrophleum chlorostachys Baill. D rugous bark E tree in northern Australian savannas H foliage F Erythrophleum lasianthum Corbishley foliage G Erythrophleum suaveolens (Guill. & Perr.) Brenan foliage and terminal inflorescences, Ntumbachusi falls, Zambia. Photo credits A Hungda (https: // tropical. theferns. info / image. php? id = Erythrophleum + fordii) B Solofo Eric Rakotoarisoa, iNaturalist (https: // www. inaturalist. org / photos / 42581094) C Bart Wursten (https: // www. flickr. com / photos / zimbart / 8212743587 / in / photolist-dvJsxn-dvJnwi) D, E, H G Mahajan (https: // alchetron. com / Erythrophleum-chlorostachys) F JMK (https: // wikiwand. com / en / Erythrophleum _ lasianthum) G MG Bingham (https: // malawiflora. com / speciesdata / image-display. php? species _ id = 126540 & image _ id = 8).

Figure 101. Tribe Erythrophleeae inflorescences, fruits and seeds A-D Spicate racemes of species of Erythrophleum with small flowers, erect sepals and petals and hairy stamen filaments A E. suaveolens (Guill. & Perr.) Brenan with a visiting fly B E. chlorostachys (F. Muell.) Baill. (Ironwood) C, D E. lasianthum Corbishley E-I Fruits and seeds E dehisced fruits of Erythrophleum suaveolens F, G ripe fruits of Erythrophleum lasianthum H, I dispersed fruits of Pachyelasma tessmannii (Harms) Harms on the forest floor, showing the flat valves and raised margins. Photo credits: A AlkalIn (https: // commons. wikimedia. org / wiki / File: Flowers _ of _ Erythrophleum _ suaveolens. jpg) B T Harley (https: // territorynativeplants. com. au / erythrophleum-chlorostachys-ironwood) C, D SAplants E Oliver Haumann, iNaturalist (https: // www. inaturalist. org / photos / 60428121) F, G JMK (https: // commons. wikimedia. org / wiki / File: Erythrophleum _ lasianthum, _ loof _ en _ peule, _ Manie _ van _ der _ Schijff _ BT, _ a. jpg) H B Wursten (https: // flickr. com / photos / zimbart / 8212726705) I T Stevart (https: // tropicos. org / ImageDownload. aspx? imageid = 100336252).

Figure 102. Distribution of Pachyelasma based on quality-controlled digitised herbarium records. See Suppl. material 1 for the source of occurrence data.