Genus Coix in Family Poaceae
In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.
Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.
Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).
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Genus Description
Suggest a correction!Coix (L.) belongs to the tribe Andropogoneae in the subfamily Panicoideae (Poaceae). Most databases treat it as a monotypic genus with Coix lacryma-jobi L. as the sole accepted species, noting extensive infraspecific variation and synonymy (POWO, 2024; WFO, 2024). The cultivated “Job’s tears” grass is widely naturalized across tropical and subtropical Asia, Africa, and the Pacific, commonly occurring in wetlands, paddies, margins of canals, and disturbed sites; the panicoid background and the distinction of C. lacryma-jobi as the nomenclatural type are standard (Clayton et al., 2006 onward).
The genus is recognized by its robust, rhizomatous or tufted habit, broad, lanceolate to ovate blades with a midrib and conspicuous ligules, and unique inflorescences composed of many sessile and pedicellate spikelet pairs aggregated on hard, beadlike involucres that persist after grain maturity. Flowers are wind‑pollinated, as typical for Panicoideae, and the fruit is a caryopsis with starchy endosperm typical of grasses; the base chromosome number is commonly reported as x=10, well supported in cultivated materials (Kellogg, 2015).
Diversity is concentrated in southern and southeastern Asia, with extensive cultivation and naturalization elsewhere; many regional forms have been described, but current consensus reduces the genus to one species (POWO, 2024). Habitats span lowland wetlands to open wet grasslands; the beadlike involucres confer remarkable dispersal persistence in hydrological corridors, though formal dispersal syndromes have not been experimentally documented.
Major recent treatments retain the monotypic circumscription, acknowledging that forms once recognized as species (e.g., C. aquatica Roxb.) and cultivated races are encompassed within C. lacryma-jobi (POWO, 2024; WFO, 2024). Phylogenetic analyses place Coix squarely in Andropogoneae without challenging its tribal placement, though intergeneric resolution within the tribe remains incompletely resolved (GPWG II, 2012).
Human relevance is largely horticultural and cultural: the glossy, hard involucres are used for jewelry and crafts, the grain is edible in parts of Asia, and the species is grown as an ornamental, particularly in water‑garden displays. Some populations behave as weeds in wet agricultural systems, though comprehensive invasiveness assessments vary regionally.
Conservation concerns focus on habitat loss in wetland margins and reduced genetic diversity in heavily cultivated lines; further population‑level sampling across South and Southeast Asia would refine taxonomic and ecological understanding.
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Coix aquatica (Roxb.)
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Coix gasteenii (B.K.Simon)
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Coix lacryma-jobi (L.)
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