Haplolobus H.J.Lam

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

Distribution

A genus of between 10 and 20 species distributed from Borneo to the Pacific as far east as Samoa. About 12 currently accepted species in New Guinea (10 endemic), one of which also occurs in the Solomon Islands.

Morphology General Habit

Evergreen trees to 20 m tall, bark scaly, greyish

Morphology Leaves Stipules

Stipules absent

Morphology Leaves

Leaves imparipinnate, pulvinii usually present at both ends of petiolules, margins entire, domatia sometimes present. Inflorescences axillary or pseudo-terminal with a rudimentary terminal bud. Flowers unisexual, 3-merous; calyx cupular, fused to at least halfway, lobes imbricate, persistent in fruit; petals thickened at the apex and inflexed, imbricate; stamens 6 in 2 whorls, filaments free, inserted outside the disk; disk 6-lobed, persistent in fruit; ovary 3-locular, stigma subsessile, 3-lobed. Fruits ovoid to ellipsoid, periarp thin, dry, pyrenes papyraceous, a single pyrene developing, the aborted locules strongly compressed.

Ecology

In New Guinea Haplolobus is known from rain forests and montane forests from sea level to 1780 m.

Recognition

The genus can be recognised by the domatia sometimes present in axils of veins, the 3-merous flowers with petals with a thickened, inflexed apex, the thin-walled fruit with papyraceous pyrenes and a more or less apical style remnant. The surface of the fruit remains smooth in dry material. The leaflets also have tertiary and quaternary veins without marked admedial branching (i.e., the veins do not branch toward the midrib, cf. Santiria).