Antirhea Comm. ex A.Juss.

Timothy M. A. Utteridge and Laura V. S. Jennings (2022). Trees of New Guinea. Kew Publishing. Royal Botanic Gardens, Kew

Distribution

A genus of c. 38 species distributed in Madagascar and the Mascarenes, tropical and subtropical regions of China, South-East Asia, Australia and the south-western Pacific; five species occur in New Guinea (three endemics).

Morphology General Habit

Shrubs and trees to 20 m

Morphology General

Raphides absent

Morphology General Indumentum

Indumentum often sericeous or ginger-brown

Morphology Leaves Stipules

Stipules triangular, entire, caducous

Morphology Leaves

Leaves opposite or whorled, often discolorous, tertiary venation ±scalariform, finely reticulated or finger-print-like

Morphology Reproductive morphology Inflorescences

Inflorescences axillary, ±cymose, branches spreading, flowers restricted to one side, number reduced to 1–2 in female inflorescences, bracts present or absent

Morphology Reproductive morphology Flowers

Flowers bisexual or functionally unisexual (plants monoecious or polygamodioecious), 3–4(–5)-merous; calyx tube shortly funnel-shaped, lobes triangular to linear; corolla green, cream, pale yellow or reddish, tube funnel- or salver-shaped, often sericeous on outer surface, lobes contorted to the left, spreading at anthesis; filaments short, anthers included or slightly exserted; ovary 2–12(–16)-locular; ovules pendulous, 1 per locule; style branch number equalling locule number, slightly exserted or included

Morphology Reproductive morphology Fruits

Fruit a green or red fleshy drupe or berry, ellipsoid, sometimes longitudinally ribbed, hairy or glabrous

Morphology Reproductive morphology Fruits Pyrene

Pyrenes 2–12(–16), fused into a hard mass

Morphology Reproductive morphology Seeds

Seeds ±cylindrical, pointed at apex.

Ecology

Antirhea species are found in primary and secondary habitats including coastal thickets and savannah, tall forest on alluvial deposits, hill-sides, ravines, roadsides and occasionally in swamps; from sea level to c. 1800 m.

Recognition

It can be recognised by the fine and sometimes finger-print-like tertiary venation, the ±scorpioid inflorescence branches (female inflorescences reduced to 1 or 2 flowers), the ellipsoid ribbed fruits and the fine silky hairs often present on various plant parts. The leaves often dry a distinctive olive or ginger-brown characteristic of many taxa in the tribe Guettardeae. It is most likely to be confused with Guettarda L. and Timonius from which it can be distinguished by the raphides in its leaves and its contorted corolla lobes.