| # The grass genera of the world |

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

### Coix L.

From the Greek koix, a kind of palm.

Including Lacryma Medik, Lacryma-jobi Ort., Lacrymaria Fabric., Sphaerium Kuntze

Habit, vegetative morphology. Annual to perennial; stems erect or straggling, with prop-roots from the lower nodes. Culms 70–400 cm high; herbaceous; branched above. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades lanceolate; broad; 30–70 mm wide; cordate, or not cordate, not sagittate; flat; without cross venation; persistent; rolled in bud. Ligule present; an unfringed membrane to a fringed membrane.

Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only, or male-only. The male and female-fertile spikelets on different branches of the same inflorescence (in different but apposed, spiciform racemes within the pistillate sheath). The spikelets overtly heteromorphic. Plants outbreeding. Apomictic, or reproducing sexually (?).

Inflorescence. Inflorescence paniculate (but peculiar - see below); spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs (the partial inflorescences of peculiar form, on flattened peduncles, in leafy panicles). Spikelet-bearing axes very much reduced (the female ‘raceme’ usually represented by three spikelets, enclosed in a globose, hardened involucre or ‘pistillate sheath’, separated from the male raceme by a prophyll at its base. The male raceme exserted on a peduncle through the apex of the involucre); disarticulating; falling entire (within its involucre). Spikelets not secund; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations (in both male and female racemes). Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets of the female racemes female-only. The ‘longer’ spikelets of the female racemes female-only, or sterile.

Female-sterile spikelets. Male spikelets in pairs or triads, several per disarticulating raceme. Dorsally compressed, with two florets, both male or the lower sterile. Rachilla of male spikelets terminated by a male floret. The male spikelets with glumes; with proximal incomplete florets, or without proximal incomplete florets (the lower floret sterile or male); 2 floreted. The lemmas awnless. Male florets 1, or 2.

Female-fertile spikelets. Spikelets falling with the glumes. Rachilla terminated by a female-fertile floret.

Glumes two; more or less equal; long relative to the adjacent lemmas; pointed; awnless; very dissimilar (both beaked; the lower subglobose, hyaline below, subcartilaginous above; the upper narrower, strongly keeled, subhyaline). Lower glume not two-keeled; flattened on the back; not pitted; relatively smooth; many nerved. Upper glume 11 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 3–7 nerved; decidedly firmer than the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas deltoid; less firm than the glumes to similar in texture to the glumes (similar to the upper glume, but less strongly keeled; very thin and hyaline beneath the beak); not becoming indurated; entire; pointed; mucronate (beaked); hairless; carinate (but less conspicuously so than the G2); 3–5 nerved. Palea present; conspicuous but relatively short (broad, beaked); entire (subulate-beaked); not indurated (hyaline below); 2-nerved. Lodicules absent. Stamens 0 (or 3 staminodes). Ovary apically glabrous. Styles fused (into one very long style, exserted from the hard pistillate sheath). Stigmas 2.

Fruit, embryo and seedling. Fruit medium sized; compressed dorsiventrally. Hilum short (circular or elliptical, quite large). Embryo large. Endosperm hard; without lipid; containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins overlapping.

Seedling with a long mesocotyl; with a loose coleoptile.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type to chloridoid-type (the apical cells being flimsy, but relatively wide and round-tipped, and sometimes quite short); 31–42 microns long; 12–13.5 microns wide at the septum. Microhair total length/width at septum 2.9–3.25. Microhair apical cells 18–21(–28) microns long. Microhair apical cell/total length ratio 0.46–0.67. Stomata common; 31–36 microns long. Subsidiaries predominantly triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped to dumb-bell shaped.

Transverse section of leaf blade, physiology. C4; XyMS– (but very ambiguously so: could have two PCR sheaths - need to see fresh material). PCR cell chloroplasts with reduced grana; centrifugal/peripheral. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma. Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (apart from midrib hinges, the rest of epidermis mostly more or less bulliform). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in three or more rings.

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Special diagnostic feature. Inflorescences in hard, globular 6–12 mm utricles.

Cytology. Chromosome base number, x = 5. 2n = 10, 20, and 40. 2, 4, and 8 ploid. Chromosomes ‘small’. Haploid nuclear DNA content 0.8 pg (1 species, 4x).

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Maydeae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Coicinae. 5 species.

Distribution, phytogeography, ecology. Tropical Asia.

Commonly adventive. Helophytic to mesophytic; shade species, or species of open habitats; glycophytic. Forest margins and swamps.

Economic aspects. Significant weed species: C. lacryma-jobi. Cultivated fodder: C. lacryma-jobi (Job’s Tears). Grain crop species: utricles of C. lacryma-jobi sometimes made into flour.

Rusts and smuts. Rusts — Puccinia. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - C. lacryma-jobi L.

Illustrations. • Coix lacryma-jobi and Zea mays: P. Beauv. (1812). • Coix lachryma-jobi var. stenocarpa: Hook. Ic. Pl. 18 (1888). • Coix lachryma-jobi: Gibbs Russell et al., 1990. • Coix lachryma-jobi, abaxial epidermis of leaf blade: this project.

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 15th June 2025. delta-intkey.com’.

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