Xanthomyrtus Diels

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

Distribution

A genus of 23 species, distributed from Malesia to New Caledonia; 19 species in New Guinea, absent from the Solomon Islands.

Morphology General Habit

Usually montane shrubs, may be trees to 30 m

Morphology Leaves

Leaves opposite, petioles very short or leaves subsessile, usually coriaceous, ovate to lanceolate, usually <1 cm long, but can be up to 5 cm, rounded or cordate at the base, margins often recurved, apex acuminate to obtuse, midrib and intra-marginal vein visible, other veins obscure. Inflorescence usually axillary, in few-flowered dichasia or flowers solitary. Flowers 4(–5)-merous, sessile; calyx lobes thick, erect, triangular, persistent; petals yellow, clawed; stamens 10–40 in a single whorl, anthers with an apical gland; style slender, falling early; ovary inferior, 2–3-locular; placentation axile, 10–20 ovules per locule

Morphology Reproductive morphology Fruits

Fruit a many-seeded black or red berry, globular or ellipsoid

Morphology Reproductive morphology Seeds

Seeds numerous, testa hard; embryo curved with cotyledons lying face-to-face, cotyledons wider than the hypocotyl.

Ecology

In New Guinea, Xanthomyrtus has been collected from montane and alpine forests from 700 m to above 3600 m.

Recognition

Xanthomyrtus can be recognised by the small leaves which usually have the midrib and intra-marginal vein clearly visible but other venation is often obscure, sessile, yellow, 4-merous flowers and fleshy fruit. Xanthomyrtus, like Uromyrtus and some species of Decapermum, can have dense foliage and small leaves. Xanthomyrtus can be distinguished from these genera by its yellow, usually 4-merous flowers (Uromyrtus and Decaspermum are usually 5-merous and have white or pink flowers), and the anthers tipped by a gland (Uromyrtus has connectival appendages, Decaspermum has anthers without conspicuous glands or appendages). In fruit, Xanthomyrtus can be distinguished from Decaspermum by its smooth fruits (ribbed in Decaspermum).