| # The genera of Leguminosae-Caesalpinioideae and Swartzieae |

L. Watson and M.J. Dallwitz

### Michelsonia Hauman

~ Tetraberlinia, Julbernardia?.

Type species: M. microphylla (Troupin) Hauman.

Habit and leaf form. Trees; unarmed.

Phyllotaxy distichous (at least the upper leaves so). The leaves compound; pinnate (10–16 jugate); paripinnate. The leaflets many per leaf, or many per leaf to few per leaf; small, opposite or sub-opposite; sessile to sub-sessile; unilaterally auriculate, markedly asymmetrical; pinnately veined, with a predominant ‘midrib’; without a continuous marginal nerve. Stipules membranous; not connate (free). Stipels absent.

Inflorescence and floral morphology. The inflorescences compound, terminal (or subterminal); branched; of racemose units; panicles. The flowers distichous, or not distichous. Bracteoles present; relatively large and enclosing the flower buds; absent at anthesis; valvate.

The flowers hermaphrodite; pentamerous. Hypanthium more or less absent, the androecium hypogynous. Calyx 5 (with two adaxial lobes united, the other three free); covering the rest of the flower in bud; not Swartzieae type; gamosepalous; markedly irregular. Corolla present; slightly irregular, or very irregular; 5; without greatly reduced members; polypetalous. Petals white. Disk absent. The androecium comprising 10 members; not declinate; with united members (9 being united at base, the adaxial one free); members all more or less equal in length; comprising only fertile stamens. Fertile stamens 10. Ovary shortly sessile or subsessile (with the style insertion more or less eccentric). Stigma dilated. Ovules few (only two).

Fruit, seed and seedling. Fruit a two-valved pod; valves twisting and enrolling during dehiscence; not very winged longitudinally, or not noticeably winged; becoming woody. The mature valves with conspicuous, prominent, raised venation (the valves with a distinct longitudinal lateral running more or less along the middle); conspicuous venation predominantly longitudinal. Seeds not arillate; with a straight or slightly oblique radicle.

Transverse section of lamina. Leaves with 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. Simple unbranched hairs common. 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 present; (at least some of them) thin-walled; hair feet all simple, without vertical walls. 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; medium-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 (M. microphylla). Restricted to the sub-montane eastern Congo.

Tribe. Detarieae (Amherstieae of Cowan and Polhill 1981).

Miscellaneous. Illustrations: • Michelsonia microphylla: Wieringa (1999).

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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