| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Arapatiella Rizzini & Mattos

Type species: A. psilophylla (Harms) Cowan.

Habit and leaf form. Trees; unarmed.

Phyllotaxy spiral. The leaves compound; pinnate; imparipinnate, or paripinnate; with adaxially grooved rachides. The leaflets few per leaf (2–3 jugate); opposite or sub-opposite; petiolulate. Stipules present, persistent and conspicuous in mature leaves; leafy; not connate. Stipels absent.

Inflorescence and floral morphology. The inflorescences axillary and terminal; unbranched, or branched; when branced, of racemose units; simple racemes, or panicles. The flowers distichous. Bracteoles present; small, not enclosing the flower buds; absent at anthesis; not valvate.

The flowers hermaphrodite; pentamerous. Hypanthium present; turbinate. Calyx 5; covering the rest of the flower in bud; polysepalous; members imbricate. Corolla present; 5; without greatly reduced members; polypetalous. Petals clawed; imbricate; white. The androecium comprising 10 members; comprising only fertile stamens. Fertile stamens 10. Anthers versatile, attached well above the base of the connective; dehiscing introrsely; dehiscing longitudinally. Ovary stipitate; free. Stigma dilated. Ovules numerous (6–8).

Fruit, seed and seedling. Fruit a two-valved pod; valves twisting and enrolling during dehiscence (and revolute); not becoming woody.

Transverse section of lamina. 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 not seen either adaxially or abaxially. Simple unbranched hairs common; smooth. 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; conspicuously pitted; of medium thickness. Stomata adaxially very rare. Abaxial: Abaxial stomata predominantly paracytic. Abaxial epidermis not papillate. Abaxial interveinal epidermal cell walls straight, or gently undulating and markedly sinuous in high-focus optical section; conspicuously pitted in optical section; staining normally with safranin; of medium thickness.

Pollen ultrastructure. Tectum reticulate; strongly irregularly coarse-reticulate (without a margocolpus).

Species number and distribution. 2 species (A. emarginata and A. psilophylla). Brazil.

Tribe. Caesalpinieae.

Miscellaneous. Illustrations: • Arapatiella psilophylla, e.m. scanned pollen (Graham & Barker, 1981).

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: 4th August 2019. delta-intkey.com’.

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