The genera of Leguminosae-Caesalpinioideae & Swartzieae
Type species: P. diphyllum (Harms) J. Léonard.
Habit and leaf form. Trees; unarmed.
Phyllotaxy distichous. The leaves compound; subsessile, bifoliolate; paripinnate. The leaflets few per leaf (only two); obliquely oblong to oblong-lanceolate with twisted tips, gland-tipped and with submarginal glands, opposite or sub-opposite; sessile to sub-sessile; without noticeably twisted petiolules; symmetrical or nearly so (a little unequal at the base); pinnately veined, with a predominant midrib. Stipules present, persistent and conspicuous in mature leaves; ribbed, tomentellous; connate (intrapetiolar). Stipels obscurely present (represented by a basal pair of subulate structures, otherwise interpretable as leaflet vestiges).
Inflorescence and floral morphology. The inflorescences terminal (their short branches roughened by bract scars); branched; panicles. The flowers not distichous. Bracts absent at anthesis. Bracteoles present; obovate, nerved, relatively large and enclosing the flower buds; persistent beyond anthesis; valvate.
The flowers hermaphrodite; not pentamerous throughout; departing from pentamery in the androecium. Hypanthium present (?). The perianth comprising distinct calyx and corolla. Calyx 5; polysepalous; of lanceolate sepals, more or less regular. Corolla present; very irregular (having one large, deeply bilobed and long-clawed petal with two suborbicular lobes, the other four smaller and similar to one another and to the sepals); 5; without greatly reduced members; polypetalous. Petals clawed (the large one), or sessile (the smaller ones). The androecium comprising 9 members; inserted on a short intrastaminal tube; members markedly unequal; including staminodia. The staminodia 6; much reduced. Fertile stamens 3. Anthers attached well above the base of the connective; dehiscing longitudinally. Ovary shortly stipitate; eccentric, with the stipe adnate. Stigma not dilated (hoof-shaped; style pilose at base). Ovules few (3).
Fruit, seed and seedling. Fruit a two-valved pod; valves twisting and enrolling during dehiscence; becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation not predominantly longitudinal. Seeds not arillate; with a straight or slightly oblique radicle. Cotyledons not flat; 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 absent. Laminae dorsiventral. Mesophyll without unaligned fibres or sclereids. Minor veins mainly with abundant accompanying fibres.
Leaf lamina epidermes. Epidermal crystals not seen either adaxially or abaxially. Simple unbranched hairs not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Adaxial: Adaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; not conspicuously pitted; thin. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted in optical section; staining normally with safranin; thin.
Pollen ultrastructure. Tectum striate; pole to pole striate. Length of colpi greater than one half pole to pole distance.
Species number and distribution. 1 species (P. diphyllum). Tropical Africa.
Tribe. Detarieae (Amherstieae of Cowan and Polhill 1981); Amherstieae clade of Bruneau et al. (2008).
Miscellaneous. Illustrations: • P. diphyllum: Aubréville, Flore du Gabon (1968).
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’.