Sphenopus Trin.
From the Greek sphen (wedge) and pous (foot), in reference to the distally thickened pedicels.
Habit, vegetative morphology. Annual; caespitose. Culms (4–)7–30 cm high; herbaceous; 1–3 noded. Culm nodes exposed, or hidden by leaf sheaths; glabrous. Culm internodes hollow. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Sheaths not keeled, terete. Leaf blades linear; narrow; 0.3–0.6 mm wide (in S. divaricatus); flat to folded (to almost filiform); without cross venation; persistent; an unfringed membrane; not truncate; 0.6–3.4 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (with numerous, very small spikelets); open; with conspicuously divaricate branchlets; with capillary branchlets to without capillary branchlets. Primary inflorescence branches borne distichously. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; long pedicellate (the pedicels claviform).
Female-fertile spikelets. Spikelets 1.5–2.8 mm long; elliptic; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous or minutely aculeolate); the rachilla extension naked. Hairy callus absent. Callus short; blunt (glabrous).
Glumes two; minute to relatively large (G1 0.2–0.4 mm long, G2 0.5–0.9 mm in S. divaricatus); very unequal; shorter than the spikelets; shorter than the adjacent lemmas; not pointed (emarginate, truncate or rounded); awnless; carinate; very dissimilar to similar (hyaline to membranous, rounded to emarginate, the lower smaller). Lower glume 0 nerved, or 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 2–7. Lemmas similar in texture to the glumes (membranous, with hyaline margins wider above); not becoming indurated; entire; pointed, or blunt; awnless; hairless; glabrous; non-carinate (but keeled on all three veins); 3 nerved; with the nerves non-confluent. Palea present; relatively long; tightly clasped by the lemma; entire, or apically notched; thinner than the lemma to textured like the lemma (hyaline); 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; glabrous; not toothed. Stamens 3. Anthers 0.2–0.6 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea, or free from both lemma and palea; small (1–1.2 mm long in S. divaricatus); oblong or ellipsoid; shallowly ventrally longitudinally grooved; compressed laterally, or not noticeably compressed. Hilum short. Endosperm liquid in the mature fruit, or hard; with lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous, or lacking. 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, or having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs (usually), or not paired (solitary); silicified (when paired), or not silicified. Costal short-cells predominantly paired. Costal silica bodies horizontally-elongated smooth, or tall-and-narrow, or crescentic; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size. Midrib conspicuous (rarely), or not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (not apparent in the large-celled epidermis, save for the ‘midrib hinges’). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 6 and 7. 2n = 12 and 24. 2 and 4 ploid. Chromosomes ‘large’.
Taxonomy. Pooideae; Poodae; Poeae.
Distribution, ecology, phytogeography. 2 species; Mediterranean to western Asia. Commonly adventive. Species of open habitats; halophytic. Saline soils and maritime sand.
Holarctic and Paleotropical. Boreal and Tethyan. African. Euro-Siberian. Macaronesian, Mediterranean, and Irano-Turanian. Saharo-Sindian. European.
Rusts and smuts. Smuts from Tilletiaceae. Tilletiaceae — Tilletia.
References, etc. Leaf anatomical: this project.
Special comments. Fruit data wanting.
Illustrations. • General aspect. • Inflorescence detail. • Inflorescence detail. • Spikelet
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
