Pachystylus K.Schum.

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

Distribution

A small New Guinea endemic genus of two species: Pachystylus henningsianus Warb. and P. zippelianus (Miq.) Bremek.; very few collections of the former are known.

Morphology General Habit

Shrubs or small trees to 8(–10) m; branching distinctive ‘Pavetta-type’ (see Pavetta account) but not as curved, branches rounded or 4-angular

Morphology General

Raphides absent

Morphology Leaves Stipules

Stipules shortly connate at base, keeled, triangular, apex acuminate, caducous

Morphology Leaves

Leaves without bacterial nodules. Inflorescences usually terminal, several flowered, compact, bracts and bracteoles present, edges sometimes drying papery, leaf pair subtending inflorescence is reduced or anisophyllous

Morphology Reproductive morphology Flowers

Flowers bisexual and unisexual (plants polygamodioecious), 5-merous; calyx pubescent, tube short, lobes triangular to slightly ovate; corolla contorted to the left in bud, white, cream or pale yellow, tube cylindrical, inner surface hairy, lobes may be reflexed or spreading at anthesis; stamen filaments short, adnate to upper part of tube, anthers long, exserted; ovary pubescent, 2-locular, ovules 1–3 per locule; style and stigma exserted, stigma elongate and thickened towards apex, apex bifid

Morphology Reproductive morphology Fruits

Fruit subglobose, often shiny, green or yellow, dying blackish; seeds 2–6 with an adaxial hilar cavity excavation.

Ecology

Distributed in lowland to lower montane forest, and in riverine vegetation on a variety of substrates including peaty, rocky and alluvial soils.

Recognition

The leaves of Pachystylus zippelianus have been noted for their production of a red dye that is used to dye bilums in some communities. It closely resembles Tarenna (some authors consider the two to be congeneric) but can be recognised by the supposedly unisexual flowers and stipules which can be fairly large.