Description: Perennial herbs, often ± woody at base, decumbent or spreading, with flowering branches usually erect.
Leaves pinnate, upper leaflets largest, leaflets lobed to toothed; stipules sheathing at base, fused to petiole.
Flowers small, sessile, clustered in globose heads or interrupted spikes, peduncles elongating in fruit, bracts present. Hypanthium tubular, persistent in fruit and developing spines that are barbed at apex. Epicalyx absent. Sepals usually 4. Petals absent. Stamens 2–10. Carpel generally solitary.
Fruit an achene tightly enclosed in the spiny hypanthium; hypanthia clustered and often forming a spiny burr-like head.
Distribution and occurrence: World: 100 species, mainly Southern Hemisphere. Australia: 7 species, all States except N.T.
Orchard (1969) considered A. ovina Cunn. s. lat. to be an extensive hybrid complex with A. echinata and A. agnipila as parent species. Virtually all possible character combinations exist with not much evidence of geographical segregation. In his treatment the various combinations are treated as varieties and in many instances identification to variety is difficult.
Text by G. J. Harden & A. N. Rodd
Taxa not yet included in identification key
| ||Key to the species|| |
|1||Flowers and fruiting hypanthia all arranged in globose, terminal heads; stolons present||2|
|Flowers and fruiting hypanthia in long interrupted spikes or in heads with 3 or 4 flowers scattered on the stem below; stolons usually absent||3|
|2||Leaflets at least twice as long as wide, lower surface glaucous and densely to sparsely pilose with appressed hairs; fruiting peduncle pubescent||Acaena novae-zelandiae|
|Leaflets less than twice as long as wide, lower surface not glaucous, glabrous except for a few hairs along veins; fruiting peduncle more or less glabrous or sparsely pilose|
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|Acaena sp. A sensu Harden (1990)|
|3||Flowers and fruiting hypanthia in globose or ovoid heads with 3 or 4 scattered on stems below, 4–6 slender spines at the apex, and several smaller ones on the body of the fruiting hypanthia; stolons often present||Acaena x anserovina|
|Flowers and fruiting hypanthia in elongated interrupted cylindrical spikes; fruiting hypanthia with many spines, equal or unequal, scattered over the entire surface; stolons absent|
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|4||Leaflets densely and evenly appressed-pilose on the lower surface, moderately appressed-pilose on upper surface; fruiting hypanthia ovoid, more or less wrinkled, lacking longitudinal ridges, spines slender||5|
|Leaflets with hairs confined to the main veins on the lower surface, glabrous or sparsely pilose above; fruiting hypanthia ovoid with all spines slender or with 3 or 4 longitudinal ridges formed by concrescence of the thickened bases of the largest spines; spines always unequal|
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|5||Spines on fruiting hypanthia unequal, 3–6 much longer than the rest||Acaena ovina|
|Spines of fruiting hypanthia more or less equal|
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