Stem anatomy of Acanthosicyos horridus (Cucurbitaceae)

The leafless, green stemmed, non-succulent plant Acanthosicyos horridus (Cucurbitaceae) is an endemic species of the foggy Namib Desert. The transverse stem section shows 15 white ridges alternately with 15 green furrows. The complete cylinder of extraxylary fibres in the primary cortex is typical of the cucumber family. Fifteen bicollateral vascular bundles each are situated in an inner and an outer circle. Secondary growth is typical for the vine type. Articulated ramified sap filled idioblasts are a special feature not described until now in A. horridus.