Michelsonia microphylla (kasisi)

Michelsonia microphylla is limited to the sub-montane area at the eastern rim of the Congo basin in the Democratic Republic of Congo, where it once formed extensive, single species stands. However, it is now considered to be rare. Michelsonia microphylla forest has been recorded as interdigitating (interlocking like the fingers of two clasped hands) with forest dominated by Gilbertiodendron dewevrei, another leguminous tree species. In the hilly terrain where they grow, trees of M. microphylla occupy the upper slopes and hilltops, whereas trees of G. dewevrei are found on the lower slopes, particularly in the valley bottoms.

A forest tree up to 30 m tall, Michelsonia microphylla has leaves that bear 10–16 pairs of leaflets. The small flowers are arranged in compound inflorescences (flower-bearing structures). Flowers have five white petals, each about half a centimetre long. The pods (fruits) are woody, flat, broader towards the tip, measure up to about 10 cm long and 7 cm wide and are heavy, sinking in water even when dry. The glossy, brown faces of the pods each have a distinct nerve running lengthways at or just above the midpoint of each face of the pod.

Line drawing of Michelsonia microphylla taken from 'Legumes of the World' (Illustration: Pat Halliday)

Michelsonia microphylla has not been formally assessed according to IUCN Red List criteria. The distribution described above is based on historical records from collections made almost exclusively in the 1940s and 1950s. During that period there was extensive logging activity in the Congo basin that is thought to have been responsible for a dramatic reduction in the species’ range. The most recent herbarium collection of Michelsonia microphylla was made in 1972. Attempts to locate individuals in places where they had previously been recorded have so far been unsuccessful.

Reports suggest that historically the timber was considered of good quality and easy to process.

Pressed and dried specimens of Michelsonia microphylla are held in Kew’s Herbarium where they are available to researchers by appointment.

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