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The grass genera of the world

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

Chrysochloa Swallen

Including Bracteola Swallen

Habit, vegetative morphology. Annual, or perennial; stoloniferous, or caespitose. The flowering culms leafy. Culms 10–75 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves mostly basal; non-auriculate. Leaf blades narrow; 3–6 mm wide (strap-shaped, the apices blunt); not setaceous; flat, or folded, or rolled; without abaxial multicellular glands; without cross venation; persistent. Ligule a fringed membrane; truncate. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality (save that terminal spikelets may be reduced).

Inflorescence. Inflorescence of spicate main branches; digitate, or subdigitate (a terminal, spreading-ascending verticil of racemes). Primary inflorescence branches 2–6. Rachides trigonous. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes spikelike; persistent. Spikelets solitary; secund; narrowly biseriate; subsessile (appressed); imbricate; not in distinct ‘long-and-short’ combinations.

Female-fertile spikelets. Spikelets 3–5 mm long; strongly compressed laterally; disarticulating between the glumes (leaving G1 on the rachis); disarticulating between the florets; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets. Hairy callus absent.

Glumes two; more or less equal; long relative to the adjacent lemmas; hairless; pointed; shortly awned (G2 sometimes), or awnless; carinate (and G1 laterally compressed), or carinate and non-carinate (G2 sometimes rounded on back); narrow, lanceolate, membranous. Lower glume 1 nerved. Upper glume 1 nerved, or 5 nerved (C. orientalis). Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1 (male or sterile); merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (firmly membranous to leathery); not becoming indurated; entire; pointed; mucronate, or awned. Awns when present, 1; dorsal; from near the top (subapical); non-geniculate; straight, or flexuous; hairless (glabrous or scabrid); much shorter than the body of the lemma. Lemmas hairy (villous on the nerves); carinate; without a germination flap; 3 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; thinner than the lemma; not indurated (very thin); 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate (relatively long); without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea (but embraced); ellipsoid; trigonous. Pericarp fused.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (and very conspicuous, in C. hubbardiana), or absent (C. orientalis, C. hindsii); in C. hubbardiana, intercostal. Intercostal papillae in C. hubbardiana, commonly at least slightly over-arching the stomata; consisting of one symmetrical projection per cell (one thick-walled papilla in the middle of each intercostal cell in C. hubbardiana). Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals narrower, in C. hindsii and C. orientalis), or markedly different in shape costally and intercostally (C. hubbardiana with the costals much narrower, and the intercostals often short or irregular in shape); of similar wall thickness costally and intercostally (quite thin walled). Intercostal zones with typical long-cells (C. orientalis, C. hindsii), or exhibiting many atypical long-cells (the ‘long-cells’ and interstomatals often short in C. hubbardiana). Mid-intercostal long-cells rectangular (or rectagular to irregularly shaped, in C. hubbardiana); having markedly sinuous walls. Microhairs present; more or less spherical (in C. hubbardiana, about 9µ in diameter), or elongated (C. orientalis, C. hindsii); ostensibly one-celled (in C. hubbardiana), or clearly two-celled (C. orientalis, C. hindsii); panicoid-type (unambiguously, in C. hidsii and C. orientalis), or chloridoid-type (in C. hubbardiana). Microhair apical cell wall thinner than that of the basal cell and often collapsed (in C. hindsii and C. orientalis). Microhairs about 9 microns long (in C. hubbardiana), or 30 microns long (in C. hindsii). Microhair basal cells in C. hindsii, about 5 microns long. Microhair apical cell/total length ratio in C. hindsii, about 0.8. Stomata common; 18–21 microns long (in C. hubbardiana), or 25–30 microns long (in C. hindsii). Subsidiaries papillate to non-papillate (C. hindsii), or non-papillate (C. hubbardiana, C. orientalis); predominantly triangular (often truncate-triangular in C. hubbardiana). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or common to absent or very rare; when seen, not paired (solitary); silicified to not silicified. Intercostal silica bodies absent to imperfectly developed. Short intercostal prickles common in C. orientalis, but neither macrohairs nor prickles seen in C. hubbardiana. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired (the short-cells often tending to be quite long in C. hubbardiana and C. orientalis). Costal silica bodies present in alternate cell files of the costal zones; exclusively saddle shaped (in C. hubbardiana), or ‘panicoid-type’ (C. hindsii, C. orientalis); in C. hindsii and C. orientalis, cross shaped to dumb-bell shaped (seemingly mostly crosses and short dumb-bells).

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Leaf blade adaxially flat. Midrib conspicuous (via a large, narrow abaxial keel); having a conventional arc of bundles (a large median and a smaller lateral on either side); with colourless mesophyll adaxially (midrib and adjoining lamina adaxially colourless). Bulliforms present in discrete, regular adaxial groups (between all the lamina bundles); associated with colourless mesophyll cells to form deeply-penetrating fans (the fans large, rather irregularly shaped). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (most bundles with scanty girders; submarginal bundles with heavy I-shaped combinations). Sclerenchyma all associated with vascular bundles.

Cytology. 2n = 14.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 5 species.

Distribution, phytogeography, ecology. Tropical Africa.

Species of open habitats. Seasonally waterlogged ground.

References, etc. Leaf anatomical: this project for C. hubbardiana and C. orientalis. Observations on C. hindsi provided by Christine de Jong, 2005.

Special comments. The remarkable differences between epidermal preparations referred to C. hubbardiana on the one hand, and those referred to C. orientalis and C. hindsii on the other, seem taxonmically improbable and evidently call for further investigation. Illustrations. • C. hubbardiana: Jacques-Félix, 1962. • Chrysochloa hubbardiana, abaxial epidermis of leaf blade: this project. • Chrysochloa hubbardiana, abaxial epidermis of leaf blade: this project. • Chrysochloa hubbardiana - abaxial epidermis of leaf blade, papillae and silica bodies: this project


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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: 13th November 2017. delta-intkey.com/grass’.

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