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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Pterogyne Tul.

Type species: P. nitens Tul.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; pinnate; paripinnate (but with a well developed rachis extension); with adaxially grooved rachides (broadly so). The leaflets many per leaf, or few per leaf; oblong, shining, mostly alternate; without noticeably twisted petiolules; symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’; without a continuous marginal nerve. Stipules minute, absent or early caducous or very inconspicuous in mature leaves; membranous. Stipels absent.

Inflorescence and floral morphology. The inflorescences catkin-like, axillary; unbranched; short and lax simple racemes. The flowers not distichous. Bracts small but broad, scale-like, deciduous, absent at anthesis. Bracteoles absent.

The flowers small; hermaphrodite; pentamerous; coloured. Hypanthium present (very short), or absent, the androecium hypogynous. Calyx 5; not covering the rest of the flower in bud; polysepalous; more or less regular (the narrow, sub-petaloid sepals subequal); members imbricate. Corolla present; slightly irregular; 5 (slightly exceeding the calyx); without greatly reduced members; polypetalous. Petals subequal, imbricate; imbricate-ascending; yellow. The androecium comprising 10 members; not declinate; members all free of one another; comprising only fertile stamens. Fertile stamens 10. Anthers attached well above the base of the connective; dehiscing horseshoe-shaped, laterally; dehiscing longitudinally. Ovary adaxially winged, stipitate; free. Stigma terminating the short style, truncate, slightly dilated, or not dilated. Ovules solitary.

Fruit, seed and seedling. Fruit indehiscent (samaroid, with one basal seed); curved; winged distally to the single seed (the wing thin, rigid, falcate-oblong with incurved veins); compressed, leathery, not becoming woody. Seeds non-endospermic; with a straight or slightly oblique radicle; amyloid-negative.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses common in 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 common; scabrid. No compound or branched eglandular hairs seen. Capitate glands not seen. Hooked hairs not seen. Cassieae-type leaf pseudo-glands not seen. Expanded and embedded hair-feet absent. Basally bent hairs present. Adaxial: Adaxial interveinal epidermal cell walls straight in optical section; not conspicuously pitted; thick. Stomata adaxially very rare. Abaxial: Abaxial stomata not predominantly paracytic (cyclocytic). Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating; not conspicuously pitted in optical section; scarcely staining with safranin, or staining normally with safranin; of medium thickness.

Wood anatomy. Wood without septate fibres; storied, or not storied. Intervascular pits very small.

Cytology. Basic chromosome number, x = 10. 2n = 20.

Species number and distribution. 1 species (P. nitens). Brazil, Paraguay, northern Argentina.

Tribe. Caesalpinieae.

Miscellaneous. Illustrations: • P. nitens: Fl. Brasiliensis 15 (1870).

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.’.