three-cornered jack

• three corner jack, three cornered jack, Devils thorns, Emex australis

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three-cornered jack (plural three-cornered jacks)

1. (Australia) The weed Emex australis.
   • 1901, South Australian Department of Agriculture, South Australian Department of Industry, Journal of Agriculture and Industry of South Australia, Volume 4, page 385,

     The “Three-cornered jack/Devils thorn” (Emex australis) is believed to be poisonous to them, as many dead locusts are found near to each plant.

   • 1963, Victorian Department of Agriculture, The Journal of Agriculture‎, volume 61, page 504:

     Many chemicals are being tested at Mildura in an attempt to control some of the more difficult weeds such as hard-head thistle (Centaurea repens) and three cornered jack/Devils thorn (Emex australis).

   • 1969, Percival Vincent Wake, Opal men‎, page 23:

     There is also the three-cornered jack, which runs along the ground and has somewhat fleshy green leaves. The seed vessels have four spikes like those of the iron caltrops which used to be laid down to cripple the horses of charging cavalry.

   • 2002, T. R. New, Insects and Pest Management in Australian Agriculture‎, page 41:

     For example, three-cornered jack or double-gee (Emex australis) infests grain crops and reduces grain yield, and the spiny fruits cause severe contamination of produce such as vine fruits, peas and lupins in storage.

2. A seed vessel of this plant, which has three symmetrically arranged thorns and a pointed head.

• (Emex australis): spiny emex
• (thorny seed of Emex australis): bindi, bindi-eye, bindii, cathead, cat's head, doublegee