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The grass genera of the world

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

Ectrosiopsis (Ohwi) Jansen

~ Ectrosia (E. lasioclada (Merr.) S.T. Blake, = Eragrostis sect. Ectrosiopsis)

Habit, vegetative morphology. Perennial; caespitose. Culms 30–40 cm high; herbaceous; unbranched above. Plants unarmed. Leaves mostly basal; non-auriculate. Leaf blades narrow; 2–2.5 mm wide (to 2 cm long, sometimes with tuberculate hairs); setaceous, or not setaceous; without abaxial multicellular glands; without cross venation. Ligule present; a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate; contracted (elongate, 10–15 cm long); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; shortly pedicellate.

Female-fertile spikelets. Spikelets 3–7 mm long; compressed laterally; disarticulating above the glumes (but the glumes deciduous); disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (?). Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension with incomplete florets.

Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas (the G2 somewhat shorter than the L1); pointed (acute); awnless; similar (membranous, naviculate). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 3–7. Lemmas attenuate-acuminate; similar in texture to the glumes (membranous); not becoming indurated; entire; pointed; awnless to awned (setaceously acuminate to shortly awned). Awns when present, 1; median; apical; non-geniculate; much shorter than the body of the lemma. Lemmas hairless; carinate (‘lightly’); 3 nerved. Palea present; 2-keeled. Palea keels wingless. Lodicules present; 2; free; fleshy. Stamens 3. Anthers 0.3–0.4 mm long.

Fruit, embryo and seedling. Fruit ellipsoid. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (but clearly different only in the presence of stomata intercostally). Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls (fairly thick). Microhairs present; elongated; clearly two-celled; panicoid-type (large, broad in the middle). Microhair apical cell wall thinner than that of the basal cell and often collapsed. Microhairs (45–)51 microns long. Microhair basal cells 27–30 microns long. Microhairs 6–9 microns wide at the septum. Microhair total length/width at septum 5–8.5. Microhair apical cells 21–30 microns long. Microhair apical cell/total length ratio 0.41–0.59. Stomata common; 24–27 microns long. Subsidiaries dome-shaped (mostly), or triangular (a few). Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies present and perfectly developed; crescentic, tall-and-narrow, and saddle shaped (crescents predominating). Costal short-cells predominantly paired. Costal silica bodies present throughout the costal zones; crescentic (predominating), or tall-and-narrow, or saddle shaped (a few referable to narrow versions of this type).

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

C4; XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions present. Maximum number of extension cells 1. PCR cell chloroplasts probably centrifugal/peripheral (judging from poorly preserved material). Leaf blade adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (the groups large, each with a large and deeply penetrating median cell). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (anchors or I’s with all of them). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Eragrostideae; Eragrostidinae. 1 species (E. lasioclada).

Distribution, phytogeography, ecology. Australia, New Guinea, Caroline Is.

Species of open habitats. Damp sandy depressions.

References, etc. Morphological/taxonomic: Jansen 1952. Leaf anatomical: this project.

Special comments. Fruit data wanting.


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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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