Electronic Flora of South Australia
Electronic Flora of South Australia
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Electronic Flora of South Australia genus Fact Sheet

Family: Zygophyllaceae

Citation: L., Sp. Pl. 386 (1753).

Derivation: Greco-Latin for the 4-pointed military instrument called the 'caltrop', employed to lame advancing cavalry, with 3 of the points always upturned; a name also applied to T. terrestris.

Synonymy: Not Applicable

Common name: Caltrops.

Annual, biennial or perennial, usually prostrate herb, rarely erect shrub; leaves paripinnate, opposite (pairs unequal) or alternate.

Flowers solitary, pseudoaxillary, pedicellate; sepals and petals 5, imbricate, caducous; stamens 10 (rarely by abortion fewer), the outer opposite the petals; filaments filiform or subulate, without appendages; disk fleshy, annular, 10-lobed; nectariferous glands episepalous, 5 between the calyx and corolla and 5 between the inner stamens and ovary; ovary 5-lobed, 5-celled, with 2-5 ovules in each cell; style simple, cylindrical, 5-ridged, deciduous; stigma terminal, pyramidal or globose.

Fruit separating into 5 (sometimes reduced by abortion to 3 or 4) woody indehiscent usually spiny cocci, when winged the wings are in the position of the extended walls segregating the cells and split longitudinally, so that each coccus retains 2 (halves of) wings at its flanks; seeds without endosperm, separated by transverse or oblique septae which develop after fertilisation.

Distribution:  About 25 species of the Old World of which 1 is introduced in North and South America; in Australia about 10 species; on sandy or stony ground, often on gravelly roadsides.

Biology: No text

Taxonomic notes: Fully ripe fruits are needed for the recognition of the species. (El Hadidi (1978) Taeckholrnia 9:59-66.)

Key to Species:
1. Fruit with 5 vertical wings; cocci with 1 pair of short conical prickles
T. macrocarpus 3.
1. Fruit without wings, with prickles, or muricate
2. Fruit strongly depressed, stellate, with 5 stout spreading spines,flat at the base, conical at the apex
T. astrocarpus 1.
2. Fruit not depressed, more or less globular, with 10 or more distinct prickles, rarely only muricate
3. Prickles of fruit few; each coccus with 2 divergent spines on their back above the middle and 2 shorter conical spines near the base directed downwards; flowers small, 6-15 mm across; sepals 3-5 mm long; petals 3-10 mm long
T. terrestris 5.
3. Prickles of fruit numerous, covering the back of each coccus, or rarely cocci only muricate
4. Flowers to 2.5 cm across; sepals 5-8 mm long; petals 10-13 mm long; fruit to 2 cm across; cocci covered on their back with short conical hairy prickles, usually only 2-3 (rarely to 8) mm long, sometimes merely muricate
T. occidentalis 4.
4. Flowers to 5 cm across; sepals 12-15 mm long; petals 25-30 mm long; fruit 3.5-4 cm across; cocci with long (to 15 mm) and short (c. 5 mm) spines on their back
T. hystrix 2.

Author: Not yet available

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