It is the earliest diverging member of its family and has a number of traits that are unique within it, such as non-succulent leaves and a lack of raphides (a particular form of calcium oxalate).

They bear six fertile stamens which have no hairs on their filaments and release pollen from a slit that develops from top to bottom, known as longitudinal dehiscence.

The seeds are arranged in a single row within the capsule and show a small point-like scar where previously attached to the carpel (i.e. the hilum is punctiform).

They lack glandular microhairs, which are small trichomes thought to be involved in the lubrication of freshly expanding leaves, which again all of the plants' siblings have.

Finally, they have yellow flowers and glandular hairs on the leaves and stems; these characters are not unheard of in the rest of the family, but both are very rare.