Kairoa Philipson

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

Distribution

A small genus of four species endemic to New Guinea.

Note

The genus has been expanded recently to include Kairoa villosa (Kaneh. & Hatus.) S.S.Renner & W.N.Takeuchi, previously placed in the monotypic genus Faika Philipson (see Renner & Takeuchi 2009).

Morphology General Habit

Small trees or sparsely branched shrubs to c. 5 m, stems and branches with prominent irregular longitudinal ridges of cork

Morphology Leaves

Leaves opposite, margin toothed, densely hairy to glabrous. Inflorescences axillary, fasciculate or single

Morphology Reproductive morphology Flowers

Staminate flowers cream coloured, receptacle at first globose with a small ostiole bounded by 8 tepals (in 2 double pairs), at anthesis splitting to form an open bowl-shaped flower with 4–6 radiating lobes, fleshy; stamens c. 25–100+, inserted over the surface of the receptacle; anthers opening by 2 longitudinal slits, filament very short Flowers unisexual, plants monoecious or dioecious

Morphology Reproductive morphology Flowers Gynoecium Pistil

Pistillate flowers receptacle oblate, with an ostiole surrounded by 2–5 pairs of 4 tepals, splitting into broad segments; the upper part of the receptacle abscising by a circular split after anthesis, stigma short sessile; carpels 8–numerous, sessile, with a very short style

Morphology Reproductive morphology Fruits

Drupes black when mature, numerous, ovoid, sessile on an enlarged fleshy receptacle (orange at maturity).

Ecology

Kairoa species are found in the undergrowth of lowland rain forests of up to 1250 m.

Recognition

Kairoa can be recognised by the toothed leaves, axillary fascicles borne on a short peduncle bearing crowded minute bracts, staminate flowers which are relatively large for the family and with numerous stamens, and black drupes on an orange fruiting receptacle. Kairoa suberosa is distinct with the older stems being very corky and deeply fissured - a useful field character for the species. Kairoa villosa is very distinct on account of the villose young branches, lamina and venation (especially below), the solitary flowers, and hairy drupes which are black when mature.