Coix is a small genus of grasses (family Poaceae, order Poales) native to Asia and Australia. GBIF's backbone taxonomy places it as an accepted genus within Poaceae, alongside its historical association with the tribe Maydeae — a placement now understood to be polyphyletic, meaning Coix was once grouped with maize relatives on the basis of shared characteristics that do not reflect a single common ancestry. The genus has also, at various points, included species now reclassified into the related grass genera Chionachne, Polytoca, and Tripsacum.
The best-known member of the genus is Coix lacryma-jobi, widely known as Job's tears, named for its hard, tear-shaped, pearly seed coverings. Its cultivated variety, Coix lacryma-jobi var. ma-yuen, is grown across many warm regions of the world as a source of food, traditional medicine, and ornamentation — the beadlike fruits are commonly strung for jewelry and rosaries. Beyond lacryma-jobi, the genus includes Coix aquatica, found from southern China through the Indian subcontinent, Indochina, and Peninsular Malaysia (and naturalized in New Guinea), and Coix gasteenii, restricted to northern Queensland, Australia. Coix lacryma-jobi itself has a broad native range across China, the Indian subcontinent, and Southeast Asia, and has become naturalized well beyond that range — in other parts of Asia as well as southern Europe, Africa, the Americas, and various oceanic islands, reflecting its long history of cultivation and spread by people.
At the molecular level, members of Coix produce a distinctive variety of α-zein storage prolamins that have undergone unusually rapid evolutionary divergence from those of closely related grasses, driven by changes in gene copy number — a feature of interest in comparative studies of maize and its relatives.
Etymology
The genus name Coix derives from Ancient Greek κόϊξ (koix), a term that originally referred to the doum palm (Hyphaene thebaica) — the fruits of the doum palm resemble the hard, bead-like diaspores of Coix.
Distribution
Coix species occur across Asia and Australia. Coix aquatica is native from southern China through the Indian subcontinent, Indochina, and Peninsular Malaysia (naturalized in New Guinea); Coix gasteenii is restricted to northern Queensland, Australia; and Coix lacryma-jobi ranges natively across China, the Indian subcontinent, and Southeast Asia, with naturalized populations elsewhere in Asia, southern Europe, Africa, the Americas, and various oceanic islands.
Taxonomy Notes
Coix was formerly placed in the tribe Maydeae, a grouping now understood to be polyphyletic. The genus has also formerly included species now reclassified into Chionachne, Polytoca, and Tripsacum.
Cultural Uses
The variety Coix lacryma-jobi var. ma-yuen (Job's tears) is cultivated across many warm regions of the world as a source of food, traditional medicine, and ornamentation, including use of its hard, bead-like fruits in jewelry and rosaries.
