# Amphistemon

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***Amphistemon*** is a [genus](/source/Genus) of 2 species of [flowering plants](/source/Flowering_plant) in the [family](/source/Family_(taxonomy)) [Rubiaceae](/source/Rubiaceae). It is described by [Inge Groeninckx](/source/Inge_Groeninckx) in 2010 based on a molecular analysis of the *[Hedyotis](/source/Hedyotis)*-*[Oldenlandia](/source/Oldenlandia)* group.[1] 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](/source/Hedyotis)*-*[Oldenlandia](/source/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.[1]

## Distribution and habitat

It is endemic to southwestern and western [Madagascar](/source/Madagascar) and is found in dry spiny forest-thicket and coastal bushland.[1]

## Taxonomy

According to molecular analysis of the genus, it is found to be closely related to *[Astiella](/source/Astiella)* of the species-group *[Hedyotis](/source/Hedyotis)*-*[Oldenlandia](/source/Oldenlandia)*.[1]

## Species

- *[Amphistemon humbertii](/source/Amphistemon_humbertii)* [Groeninckx](/source/Inge_Groeninckx)
- *[Amphistemon rakotonasolianus](/source/Amphistemon_rakotonasolianus)* [Groeninckx](/source/Inge_Groeninckx)

## References

1. Groeninckx I, De Block P, Robbrecht E, Smets E, Dessein S. 2010. "*Amphistemon* and *Thamnoldenlandia*, two new genera of Rubiaceae (Spermacoceae) endemic to Madagascar." *Botanical Journal of the Linnean Society* 163: 447-472.

## External links

- [*Amphistemon* in the World Checklist of Rubiaceae](http://apps.kew.org/wcsp/qsearch.do?plantName=Amphistemon)

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Adapted from the Wikipedia article [Amphistemon](https://en.wikipedia.org/wiki/Amphistemon) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Amphistemon?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.