Belongs to the ditypic genus: A. humbertii and A. rakotonasolianus; Subfamily: Rubioideae; Tribe: Spermacoceae.

Much-branched subshrub with main branches erect, up to 0.5 m tall; stems quadrangular. Leaves decussate, sessile, fused with the stipule base, simple. Stipules fimbriate, persistent. Inflorescences terminal or pseudo-axillary, simple or compound dichasia, three- to many-flowered. Capsules broadly obovate. Seeds elliptic, ovate or broadly ovate in outline; wing present as narrow.

A. humbertii differs from A. rakotosolianus in its habit and winged seeds. This genus differs from others by the position of insertion of the stamens at twolevels in the corolla tube. Phylogenetically, it forms a robust clade with the Malagasy monotypic genera Thamnoldenlandia, Astiella and the ditypic genus Phialiphora (Janssens & al., 2016).

Flowering time:  February

Population: 8 subpopulations

Lower elevation limit: 2 metres

Fruiting time: 

Trends:

Upper elevation limit: 740 metres