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The genera of Leguminosae-Caesalpinioideae & Swartzieae

L. Watson and M.J. Dallwitz

Stachyothyrsus Harms

Kaoue Pellegr.

Type species: S. staudtii Harms.

Habit and leaf form. Trees; without specialized ‘short shoots’; unarmed.

Phyllotaxy spiral. The leaves compound; mostly bipinnate (with two pairs of pinnae, rarely with a few pinnate only); with opposite or sub-opposite pinnae; with opposite or sub-opposite leaflets (these sometimes minutely gland-dotted). The leaflets without noticeably twisted petiolules; symmetrical or nearly so; pinnately veined, with a predominant ‘midrib’. Stipels absent.

Inflorescence and floral morphology. The inflorescences terminal; unbranched, or branched; of racemose units; simple racemes (these long-pedunculate, slender and spikelike), or panicles (then in large, pyramidal, long and many-flowered spikes). The flowers not distichous. Bracteoles absent; absent at anthesis.

The flowers small; hermaphrodite; pentamerous. Floral tube length relative to total hypanthium + calyx length about 0.5. Hypanthium negligible or absent, the androecium hypogynous. Calyx 5; not covering the rest of the flower in bud; gamosepalous; members imbricate. Corolla present; regular to slightly irregular (the petals subequal); 5; without greatly reduced members; polypetalous. Petals imbricate; imbricate-ascending. The androecium comprising 10 members; not declinate; members all free of one another; members markedly unequal (the alternipetalous filaments longer, distally swollen); comprising only fertile stamens. Fertile stamens 10. Anthers attached at the base of the connective (but basally sagittate). Ovary sessile or subsessile; free. Stigma small, not dilated. Ovules few (2–3).

Fruit, seed and seedling. Fruit a two-valved pod (1–2 seeded); straight; oblong-oblanceolate, flatened, becoming woody. The mature valves with conspicuous, prominent, raised venation; conspicuous venation not predominantly longitudinal. Seeds with a straight or slightly oblique radicle.

Transverse section of lamina. Leaves without conspicuous phloem transfer cells in the minor veins. Druses absent from the mesophyll. Mesophyll secretory cavities (gland-dots) common, or 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 not seen. No compound or branched eglandular hairs seen. Capitate glands not seen. Expanded and embedded hair-feet absent. Adaxial: Adaxial interveinal epidermal cell walls markedly sinuous in high-focus optical section; conspicuously pitted; thick. 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; thick.

Pollen ultrastructure. Tectum reticulate; finely to moderately regularly reticulate. Length of colpi greater than one half pole to pole distance (with margocolpus-like zones). Foot layer of pollen wall with obvious projections.

Species number and distribution. 3 species (S. stapfiana, S. staudtii, S. tessmannii). Tropical Africa.

Tribe. Caesalpinieae.

Miscellaneous. Illustrations: • S. staudtii: Engler, Pflanzenwelt Afrikas (1910). • S. staudtii, 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: 22nd March 2017.’.