Alternative names: Not Applicable

Description:
Herbs, subshrubs or shrubs; leaves stipulate, rarely exstipulate, simple or pinnate, rarely ternate, opposite or spirally arranged, usually somewhat fleshy.

Flowers solitary, regular, usually bisexual, solitary or in cymose inflorescences; sepals 4 or 5, imbricate, rarely valvate, often persistent; petals 3-5, imbricate or contorted, rarely valvate; stamens usually 2- or 3-times as many as the petals, the outer opposite the petals; filaments often with ligular appendages; anthers dorsifixed, latrorse; disk usually present; ovary superior, 3-5- rarely 10-12-celled, often vertically angled or winged; ovules axile, pendulous, 1 to many per cell; style simple; stigma capitate or lobed.

Fruit a loculicidal and/or septicidal capsule, an indehiscent nut, a schizocarp (splitting into cocci), or rarely a drupe; seeds with or without endosperm; embryo usually straight; radicle superior.

Distribution:  About 26 genera and 280 species, mainly in the tropics and subtropics, predominantly xero- and halophytes. In Australia 5 genera of which 1 is introduced, at least 35 species.

Biology: No text

Taxonomic notes: The family is heterogeneous, and some authors treat the 4 genera occurring in S.Aust. as belonging to 4 families: Peganaceae, Nitrariaceae, Tribulaceae and Zygophyllaceae.

Key to Genera:

1. Leaves simple
2. Leaves spirally arranged or clustered, oblong-cuneate, with very short appressed hairs; petals 5, white; stamens 10-15; fruit a fleshy drupe; dioecious or andromonoecious shrubs	NITRARIA 1.
2. Leaves opposite or in whorls of 4, 2-lobed or almost terete, glabrous; petals 3 or 4, yellow, stamens 6 or 8; fruit dry, a 4- angled or 4-winged capsule or 3-winged nut; flowers bisexual, annual herbs or subshrubs	ZYGOPHYLLUM 4.
1. Leaves pinnate, with 1 or several pairs of leaflets, or multifid
3. Leaves divided into many linear segments, spirally arranged	PEGANUM 2.
3. Leaves paripinnate, opposite or alternate
4. Leaves with 2 leaflets, glabrous, opposite; fruit without spines or tubercles, a 4- or 5-angular capsule or with 4 wings	ZYGOPHYLLUM 4.
4. Leaves with several pairs of leaflets, usually hairy, alternate or some opposite; fruit with spines or tubercles, if winged with 5 wings, separating into 5 or (by abortion) fewer hard cocci	TRIBULUS 3.

Author: Prepared by Hj. Eichler