| # The grass genera of the world |

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

### Echinolaena Desv.

Excluding Chasechloa

Habit, vegetative morphology. Annual, or perennial; rhizomatous to stoloniferous. Culms herbaceous; branched above. The branching simple. Culm nodes hairy, or glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; broad, or narrow; cordate; tending to pseudopetiolate, or not pseudopetiolate; without cross venation.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant, or all alike in sexuality; hermaphrodite, or hermaphrodite and sterile (the sessile members often aborted).

Inflorescence. Inflorescence of spicate main branches, or a false spike, with spikelets on contracted axes, or a single raceme; spicate ("a single spikelike raceme"). Primary inflorescence branches 1–5 (of pectinate ‘racemes’). Inflorescence with axes ending in spikelets (but the lower glume of the terminal spikelet simulating a rachis extension). Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary (ostensibly, by abortion), or paired; secund; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. The ‘shorter’ spikelets hermaphrodite, or female-only, or sterile. The ‘longer’ spikelets hermaphrodite.

Female-fertile spikelets. Spikelets 6–10 mm long; abaxial; compressed laterally; falling with the glumes. The upper floret conspicuously stipitate (its callus with narrow wings or scars at the base of the lemma). Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal to more or less equal; (the longer) long relative to the adjacent lemmas; lateral to the rachis; pointed; awned to awnless (acute to shortly awned); carinate to non-carinate (the nerves forming ribs); similar (tuberculate-bristly). Lower glume tuberculate (with tubercle based bristles); 3–9 nerved. Upper glume 7–9 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate; male. The proximal lemmas awnless; 5 nerved; decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes; smooth; not becoming indurated; entire; blunt; awnless; hairless; glabrous; non-carinate; having the margins inrolled against the palea; with a clear germination flap; 3–5 nerved. Palea present; relatively long; 2-nerved; keel-less. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small. Hilum long-linear.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (fairly thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present (large); panicoid-type; 75–90 microns long, or (48–)51–60(–63) microns long (in E. gracilis); 9–12 microns wide at the septum, or (7.5–)8.4–9(–9.3) microns wide at the septum (E. gracilis). Microhair total length/width at septum 5.3–8.7. Microhair apical cells 39–48 microns long, or 27–36 microns long (E. gracilis). Microhair apical cell/total length ratio 0.5–0.7. Stomata common; 57–63 microns long, or (39–)45–48(–51) microns long (in E. gracilis). Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired; not silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; cross shaped and dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma; Isachne-type. Leaf blade adaxially flat. Midrib with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 9. 2n = 60.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 6 species.

Distribution, phytogeography, ecology. Central & South America, 1 in Madagascar.

Helophytic, or mesophytic; species of open habitats. Savanna.

References, etc. Leaf anatomical: studied by us - E. gracilis Swallen, E. inflexa Chase.

Illustrations. • Echinolaena gracilis: Pohl, Flora Costaricensis (1980).

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’.

Contents