Monsonia

Monsonia, previously Sarcocaulon (fleshy stem), is a genus of annual or perennial herbs and succulent shrublets in the Geraniaceae family. The plants are erect or prostrate, the stems herbaceous or woody, cylindrical or compressed and the bark waxy, sometimes translucent.

The leaves may be alternate, sub-opposite or opposite when the pairs tend to be unequal. The blades are mostly simple and palmately veined or pinnately dissected. Some petioles may be long, persistent and spine-like, while others are short on the same plant in some cases. The spines are straight or curved and there are paired stipules present.

The flowers appear in clusters of one to fifteen from leaf axils, the clusters cyme-shaped or nearly umbels. The calyx consists of five sepals that are joined or free but persistent, often with mucros at their tips.

The corollas are radially symmetrical or actinomorphic, white, yellow or pink and toothed at the five petal tips. There are fifteen stamens, sometimes in five groups, the filaments often of unequal length. The superior ovary is usually stalkless and five-lobed, showing its five locules.

The five fruits or carpels produced from one flower are one-seeded each, their awns twisting spirally or coiling when dry, sometimes crested or bristly. The coiling happens from style elongation during fruiting into a beak-like protrusion that dries unevenly in ripening. The outer fibres of the beak-like appendage dry faster or more, causing the carpels to separate from the central axis and coil strongly, dispersing the fruits. On the ground the coiling drills into the soil, planting the seed. The seeds are brown and smooth or with finely networked surfaces.

There are about 27 Monsonia species in Africa, Madagascar and southwest Asia, 20 of them in southern Africa, growing in arid regions.

The old, dry stems of some of the plants burn slowly. They are used as candles or for lighting fires, hence the common name of Boesmanskers (Bushman’s candle) for some of the plants. Some of the monsonias feature in traditional medicine, used in the treatment of various disorders, including erectile dysfunction and heartburn.

The plant in picture is Monsonia crassicaulis (Leistner, (Ed.), 2000; Van Rooyen and Van Rooyen, 2019; Vlok and Schutte-Vlok, 2015; Manning, 2007; http://pza.sanbi.org).