Saurauia Willd.

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. 300 species distributed in the tropical and subtropical regions of Asia, Central and South America (conspicuously absent from Brazil and Africa). Approximately 100 species occur in New Guinea (most are endemic).

Morphology General Habit

Trees or shrubs to 15 m

Morphology Branches

Branches sometimes hollow

Morphology General

Sap usually absent, but sometimes recorded as exuding a sticky juice when cut

Morphology General Indumentum

Indumentum usually present on vegetative and flowering parts, type and density very variable (rarely ±glabrous)

Morphology Leaves

Leaf tertiary venation sometimes scalariform

Morphology Reproductive morphology Inflorescences

Inflorescences structure variable, 1–many-flowered, often nodding; bracts usually present, small and subtending to conspicuous and enclosing, sometimes calyptrate and caducous; bracteoles often present

Morphology Reproductive morphology Flowers

Flowers bisexual or functionally unisexual; calyx 5-merous, usually quincuncial, connate at base, indumentum density variable; corolla connate at base; stamens numerous, filaments connate and adnate to base of corolla, anthers dehiscing by apical pores; ovary (3–)5–8-locular, glabrous or hairy; styles 1–5, connate for all or part of length or free; stigmas simple to capitate

Morphology Reproductive morphology Fruits

Fruit a berry or leathery capsule partially dehiscing from the apex, glabrous or hairy

Morphology Reproductive morphology Seeds

Seeds often embedded in a mucilaginous pulp.

Ecology

In New Guinea and the Solomon Islands, a few (often widespread) species of Saurauia are found in lowland areas but by far the greatest number are found in montane vegetation with some species reaching very high altitudes to 3600 m.

Recognition

Saurauia are commonly found in disturbed vegetation such as the edges of landslides but are also found in less disturbed secondary and primary forests, and also along the edges of rivers. It is a poorly known and taxonomically difficult group at the species level but is easy to identify to genus because of the showy white, pink or red flowers which are sometimes obscured by large bracts and very variable but characteristic indumentum which varies between (and perhaps within) species: stellate, dendritic, lanate, scaly or thorny types are seen, amongst others. In dried material the indumentum is often a chaffy light or reddish brown, and raphides can be seen in leaf surfaces and on floral parts such as the petals. The corolla often falls as a unit with the stamens attached.