Citation: Gaertner, Fruct. 1:111 (1788).

Derivation: Latin operculum, a lid; alluding to the lid by which partial fruits dehisce.

Synonymy: Not Applicable

Common name: Stinkweeds.

Description:
Perennial shrublets usually with a slightly woody base and stiff terete but grooved rarely vaguely quadrangular branches; leaves opposite, with stipules connate to the leaf base to form a sheath around the nodes.

Inflorescence a thyrse or dichasium with 2 to numerous flowers more or less connate at their base to form together with the surrounding bracts a compound fruit; flowers bisexual, rarely unisexual and plants dioecious, 3- or 4-merous; calyx segments 3, persistent; corolla with a tube usually longer than the lobes, 4-merous, deciduous; stamens 4, with filaments attached to the base of the corolla tube; anthers with a terminal appendage; ovary inferior and more or less fused to other flowers, with 2 locules each with 1 ovule; style short, with long filiform stigmas.

Fruit a compound capsule dehiscing by the abscission of the apical lid of each flower or several lids are more or less fused and shed as a single unit.

Distribution:  About 15 species endemic to mainly temperate regions of Australia.

Biology: No text

Key to Species:

1. Peduncle longer than the subtending leaves; stipules with 2 or 3 large lobes; fruit dehiscing by a horizontal abscission layer	O. scabrida 2.
1. Peduncle shorter than the subtending leaves, or absent; stipules with 1 large lobe and 2 smaller points on either side; fruit dehiscing by an oblique abscission layer
2. Plants dioecious; inflorescences sessile or almost so on little- branched stems	O. turpis 3.
2. Plants monoecious; lower inflorescence with a peduncle 2-10 mm long and with apparently dichotomous branching at the same nodes
3. Aerial branches arising from several points of the underground rhizome; inflorescence with 10-18 flowers; post-fruiting capsule with 2 or 3 star-shaped cavities	O. ovata 1.
3. Aerial branches arising from one short main stem; inflorescence with 2-7 flowers; post-fruiting capsule star-shaped	O. varia 4.

Author: Not yet available