The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: P. caeruleum (Taub.) J. Léonard.
Habit and leaf form. Trees; unarmed.
Phyllotaxy spiral. The leaves compound; pinnate; paripinnate. The leaflets few per leaf ((2-)3–5 pairs of leaflets, asymmetric at bases); opposite or sub-opposite; petiolulate; with markedly twisted petiolules; markedly asymmetrical; pinnately veined, with a predominant midrib (which is more or less displaced). Stipules present, persistent and conspicuous in mature leaves; membranous; connate. Stipels absent.
Inflorescence and floral morphology. The inflorescences terminal; branched; of racemose units; subcorymbose, dense panicles. The flowers not distichous. Bracteoles present; relatively large and enclosing the flower buds; persistent beyond anthesis; valvate.
The flowers large; hermaphrodite; pentamerous, or not pentamerous throughout; departing from pentamery in the androecium. Floral tube length relative to total hypanthium + calyx length about 0.75. Hypanthium present; asymmetrically tubular. The perianth comprising distinct calyx and corolla. Calyx 5 (the posterior member longer and two-toothed); covering the rest of the flower in bud; polysepalous; markedly irregular; members imbricate. Corolla present; very irregular (with one large petal, 2 smaller and 2 small); 5; including greatly reduced members, or without greatly reduced members; polypetalous. The androecium comprising 7–10 members (usually 9); declinate; with united members (in a circle, unequally united at their bases); members markedly unequal; including staminodia. The staminodia 4–6; smaller than the fertile stamens. Fertile stamens exserted, 3, or 5 (rarely). Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary stipitate; eccentric, with the stipe adnate. Stigma conspicuously dilated.
Fruit, seed and seedling. Fruit a two-valved pod; without markedly twisting or enrolling valves; winged longitudinally; narrowly 1 winged; becoming woody. The mature valves without prominent venation. Seeds not arillate; with a straight or slightly oblique radicle; amyloid-positive. Cotyledons not flat; of Type 4; with a vascular system in one plane; epigeal.
Transverse section of lamina. Leaves with conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities absent. Adaxial hypodermis absent. Leaf girders common (the veins transcurrent). Laminae dorsiventral. Mesophyll without unaligned fibres or sclereids. Minor veins mainly with abundant accompanying fibres.
Leaf lamina epidermes. Epidermal crystals present; prisms. Simple unbranched hairs common. No compound or branched eglandular hairs seen. Capitate glands not seen. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; conspicuously pitted; thick. Stomata adaxially common and widespread. Abaxial: Abaxial stomata predominantly paracytic. Abaxial interveinal epidermal cell walls straight, or gently undulating; conspicuously pitted in optical section; staining normally with safranin; thick.
Cytology. Basic chromosome number, x = 12. 2n = 24.
Species number and distribution. 1 species (P. coeruleum - formerly Macrolobium). Tropical Africa.
Tribe. Detarieae (Amherstieae of Cowan and Polhill 1981); Amherstieae clade of Bruneau et al. (2008).
Miscellaneous. Illustrations: • P. coeruleum: Brenan, Fl. Tropical East Africa (1967).
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classification. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1993 onwards. The genera of Leguminosae-Caesalpinioideae and Swartzieae: descriptions, illustrations, identification, and information retrieval. In English and French. Version: 22nd March 2017. delta-intkey.com/caes’.