Description: Mostly annual or perennial herbs.
Leaves opposite, entire; sessile or shortly petiolate. Stipules interpetiolar, sheathing, membranous, often with a triangular lobe; margins usually fringed.
Flowers solitary or rarely few in terminal or axillary cymes, bisexual, 4-merous. Calyx globular, obloid or turbinate. Corolla tubular, funnel-form or trumpet-shaped. Stamens inserted on corolla tube; anthers mostly exserted. Ovary 4/5 to 9/10 inferior, 2-locular; style terete or filiform; stigma usually bifid, mostly exserted from corolla tube.
Fruit a capsule, ovoid to globose, 2-valved, dehiscing loculicidally or septicidally; seed usually many; surface variously patterned.
Distribution and occurrence: World: c. 200 species, tropical regions. Australia: c. 22 species (mostly endemic), Qld, N.S.W., N.T., W.A.
The 'beak' referred to in the key below is the portion of the capsule above the insertion of the persistent calyx lobes.
This group has been the subject of recent research, both in Australia and internationally. All species in Australia, other than the introduced O. corymbosa, are likely to be transfered to new or reinstated genera in the future. K.L. Gibbons
Text by T. A. James, edited by K.L. Gibbons, July 2019.
Taxon concept:
| | Key to the species | |
| 1 | Flowers in lax terminal cymes; corolla salver-shaped with tube generally 3 times the length of calyx lobes; capsule with beak equal to or extending beyond the calyx lobes; seed flattened, hilum on a longitudinal ridge on ventral surface | Oldenlandia mitrasacmoides |
| Flowers axillary, either solitary (rarely paired), in 2–7 flowered umbel-like corymbs, or rarely in lax terminal monochasial cymes; corolla tubular, campanulate or funnel-shaped with tube less than twice the length of the calyx lobes; capsule with beak included in calyx lobes; seed obconical with hilum near the centre of the ventral surface | 2 |
| 2 | Decumbent or prostrate annual herbs, divaricately branched; flowers axillary, in 2–7 flowered umbel-like corymbs or solitary; corolla with a distinct line of hairs at base of lobes | Oldenlandia corymbosa |
| Trailing, sprawling or ascending annual herbs, sparingly or much branched; flowers axillary, solitary or paired at nodes, or rarely in in lax terminal monochasial cymes (O. subulata); corolla glabrous or tube internally hairy without distinct line of hairs at base of lobes
Back to 1 | 3 |
| 3 | Capsule subglobose, 2.5–3.5 mm diameter; beak broad, calyx lobes 2–3 mm long; corolla funnel-shaped to campanulate with tube 1.5–3.5 mm long | Oldenlandia subulata |
| Capsule ovoid-globose, 1.5–3.0 mm long, 1.0–3.0 mm wide, slightly compressed; beak narrow; calyx lobes 1.0–1.5 mm long; corolla tubular to narrowly funnel-shaped with tube 0.5–1.5 mm long
Back to 2 | Oldenlandia galioides |
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