Emex australis Steinh.
three-cornered Jack
Annual herb. Stems prostrate to ascending, often reddish. Petiole = or > lamina except in uppermost lvs, to c. 10 mm long. Lamina 2.5-7 × 1.5-4.5 cm, ovate-oblong to almost oblong, entire; base truncate to subcordate; apex obtuse or subacute; ochreae initially c. 1 cm long. ♂ infl. to c. 3 cm long, much shorter towards branch ends; perianth 1.2-1.8 mm long, green. ♀ fls with perianth subtended by membranous bract; outer segments 2-4 mm long at flowering, with an outward-directed spine c. = segment; inner perianth segments exserted from outer but acuminate tip soft and much < spines. Fr. c. 1 cm long including spines, indurated and rigid; outer segments with 4 deep depressions; inner segments completely enclosing the nut; nut glossy, trigonous, c. 5 mm long.
N.: northern areas, especially from Taranaki and Poverty Bay northwards; S.: Westport, but not collected recently.
South Africa 1883
Coastal areas, mainly in waste and cultivated land on light sandy soils, sometimes in rough pasture.
FL Jul-Apr.
The unpleasant spiny frs of three-cornered Jack or spiny emex are reminiscent of the unrelated caltrops plant, Tribulus terrestris L. (Zygophyllaceae), which has been collected in N.Z. but is no longer present. Although E. australis was recorded as early as 1883 it has apparently not become very common.
