Amphistemon
# Amphistemon

Amphistemon is a genus of 2 species of flowering plants in the family Rubiaceae. It is described by Inge Groeninckx in 2010 based on a molecular analysis of the Hedyotis-Oldenlandia group. The genus name is based on the Greek 'amphi-' (=double or of two kinds) and 'stemon' (=stamen) referring to the dimorphic stamen position characteristic for this genus.

## Description

Amphistemon are erect perennial herbs or subshrubs with the unique feature in the Hedyotis-Oldenlandia group of having stamens inserted at two distinct levels in the corolla tube, the lower stamens with filaments and anthers shorter than those of the upper stamens.

## Distribution and habitat

It is endemic to southwestern and western Madagascar and is found in dry spiny forest-thicket and coastal bushland.

## Taxonomy

According to molecular analysis of the genus, it is found to be closely related to Astiella of the species-group Hedyotis-Oldenlandia.

## Species

* Amphistemon humbertii Groeninckx
* Amphistemon rakotonasolianus Groeninckx
