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The grass genera of the world

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

Euclasta Franch.

Including Indochloa Bor

Habit, vegetative morphology. Rambling annual. Culms 30–200 cm high; herbaceous; branched above. Culm nodes hairy. The shoots aromatic. Leaves not basally aggregated. Leaf blades narrow; 2–8 mm wide; flat; without cross venation.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile; overtly heteromorphic; in both homogamous and heterogamous combinations (the proximal 1–3 pairs imperfect and homogamous).

Inflorescence. Inflorescence of spicate main branches (terminal and axillary, the ‘racemes’ delicate, solitary or clustered, peduncled, 3–6 cm long); non-digitate (corymbiform or sub-paniculate), or subdigitate. Primary inflorescence branches 1–15. Rachides flattened. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes ‘racemes’; solitary to clustered; with very slender rachides (these flattened, sinuous); disarticulating; disarticulating at the joints (above, but the basal homogamous spikelets persistent). The pedicels and rachis internodes with a longitudinal, translucent furrow. ‘Articles’ linear (hyaline and glandular down the middle); not appendaged; disarticulating transversely; densely long-hairy. Spikelets paired; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite (except at the base of the raceme, where both sessile and pedicellate spikelets are male or neuter and persistent). The ‘longer’ spikelets male-only, or sterile.

Female-sterile spikelets. The pedicelled spikelets large, herbaceous.

Female-fertile spikelets. Spikelets 3.6–4 mm long; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present (minutely bearded). Callus short.

Glumes two; relatively large; more or less equal; long relative to the adjacent lemmas (much exceeding them); hairy (G1); awnless; very dissimilar (G1 truncate or obtuse and 2-keeled, the G2 naviculate and 1-keeled). Lower glume two-keeled (truncate or obtuse); not pitted; 9 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; epaleate; sterile. The proximal lemmas awnless; 0 nerved; not becoming indurated (very small, hyaline).

Female-fertile florets 1. Lemmas reduced to a linear, hyaline stipe beneath the awn; less firm than the glumes; not becoming indurated; entire; not deeply cleft; awned. Awns 1; median; apical (continuous from the stipe); geniculate; hairy; much longer than the body of the lemma. Lemmas hairless; non-carinate; without a germination flap; 1 nerved. Palea absent. Lodicules present; 2; free; glabrous; not or scarcely vascularized. Stamens 3; with free filaments. Anthers as broad as long; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae consisting of one oblique swelling per cell. Mid-intercostal long-cells having straight or only gently undulating walls (mostly, the walls thin). Microhairs present; panicoid-type; 40–54 microns long. Microhair apical cells 12–18 microns long. Microhair apical cell/total length ratio 0.32. Stomata common. Subsidiaries dome-shaped to triangular. Intercostal short-cells absent or very rare. Cushion-based macrohairs present. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; dumb-bell shaped (mostly), or nodular (some, and some tending to saddle-shaped).

Transverse section of leaf blade, physiology. C4; XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (one large median, 2–3 small laterals on either side). Bulliforms not present in discrete, regular adaxial groups (irregularly grouped). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.

Special diagnostic feature. The lower glume of the pedicellate spikelet awnless.

Cytology. Chromosome base number, x = 10. 2n = 40.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Sorghinae. 2 species.

Distribution, phytogeography, ecology. Tropical America, Africa, Madagascar, India.

Mesophytic; shade species, or species of open habitats. In partial shade, or among taller grasses.

References, etc. Leaf anatomical: Metcalfe 1960.

Illustrations. • E. condylotricha: Hook. Ic. Pl. 31 (1922). • E. condylotricha: Jacques-Félix, 1962

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: 11th December 2017.’.