Description: Annual or perennial herbs or subshrubs, glabrous, scabrous or pilose.
Leaves alternate or opposite, rarely in whorls of 3, sessile or petiolate, simple, the margins entire or toothed.
Inflorescences indeterminate, spike-like, mostly lateral. Flowers usually 4-merous, shortly pedicellate, single in the axis of bracts usually with a pair of bracteoles. Sepals and petals usually 4, sepals often with prominent basal callus, persistent in fruit. Petals hooded, keeled, usually shortly clawed. Stamens usually 8; filaments short, anthers not apiculate. Ovary incompletely 4-locular; styles mostly 4.
Fruit ovoid to semiglobose, smooth or ribbed; seed 1, occupying the entire fruit.
Distribution and occurrence: World: 41 spp., Aust., N.Z., Malesia. Aust.: 36 spp., all States.
Text by Peter G. Wilson
Taxon concept:
| | Key to the species | |
| 1 | Primary bracts of inflorescences opposite, at least towards the base | 2 |
| Primary bracts of the inflorescences alternate | 4 |
| 2 | Leaves ovate to broad-lanceolate, more than 2 mm wide | 3 |
| Leaves linear, usually 1–2 mm wide
Back to 1 | Gonocarpus salsoloides |
| 3 | Leaves and stems moderately to densely hairy with spreading, coarse hairs (often with a tuberculate base) | Gonocarpus teucrioides |
| Leaves scarcely hairy, stems with short, appressed hairs
Back to 2 | Gonocarpus montanus |
| 4 | Leaves all opposite (occasionally alternate in G. longifolius) on vegetative growth | 5 |
| Leaves all alternate; plants with rather long spreading hairs
Back to 1 | Gonocarpus elatus |
| 5 | Fruits with oblique calluses between the ribs | 6 |
| Fruits smooth or papillose between the ribs
Back to 4 | 10 |
| 6 | Stamens 8, all fertile | 7 |
| Stamens 4, opposite the sepals, rarely with 4 staminodes opposite the petals
Back to 5 | Gonocarpus humilis |
| 7 | Subshrubs with woody stems, usually more than 50 cm high | 8 |
| Perennial herbs, usually less than 35 cm high; stems herbaceous or only slightly woody
Back to 6 | 9 |
| 8 | Leaves linear-oblong; stems and leaves moderately densely covered with spreading hairs | Gonocarpus longifolius |
| Leaves ovate to oblong, stems and leaves densely covered with very short hairs
Back to 7 | Gonocarpus oreophilus |
| 9 | Leaves narrow-ovate; indumentum soft and spreading | Gonocarpus hirtus |
| Leaves lanceolate to narrow-elliptic; indumentum scabrous, appressed
Back to 7 | Gonocarpus tetragynus |
| 10 | Leaves narrow-lanceolate to elliptic; stem and leaves scabrous with sparse, appressed hairs; fruits papillose | Gonocarpus chinensis |
| Leaves ovate to circular; stem and leaves glabrous; fruits smooth
Back to 5 | Gonocarpus micranthus |
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