Schedonnardus Steud.
From the Greek schedon (near) and Nardus (another grass genus, q.v.).
Including Spirochloe Lunell
Habit, vegetative morphology. Perennial; caespitose. Culms 20–45 cm high; herbaceous; unbranched above. Culm internodes solid, or hollow. Leaves non-auriculate. Leaf blades narrow; 0.7–2 mm wide (to 5 cm long); flat (or involute); without abaxial multicellular glands; without cross venation; an unfringed membrane.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches (stiff, slender divergent spikes, remote along a common axis); deciduous in its entirety (the central axis first elongating and coiling into a loose spiral); open. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelets solitary; secund; biseriate (appressed to the concave sides of the triquetrous rachis); sessile; somewhat imbricate.
Female-fertile spikelets. Spikelets 3–4 mm long; compressed laterally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; (the upper) long relative to the adjacent lemmas (only slightly shorter than them); dorsiventral to the rachis (?); hairless; pointed; awnless; similar (lanceolate or acuminate, stiff, slightly divergent). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas acuminate; similar in texture to the glumes to decidedly firmer than the glumes (firmly membranous, rigid); entire; pointed; awnless to mucronate; hairless (glabrous to scabrid); carinate to non-carinate; 3 nerved. Palea present; relatively long (glabrous); entire; awnless, without apical setae; textured like the lemma; rigid; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Ovary glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit small (2.5–3.5 mm long); fusiform. Hilum short (?). Pericarp fused (?). Embryo large; with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata (at one end); consisting of one oblique swelling per cell (at one end of each interstomatal, and on a few of the long-cells as well). Long-cells of similar wall thickness costally and intercostally (walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type (the basal cell somewhat the longer). Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 51–52.5–57 microns long. Microhair basal cells 36 microns long. Microhairs 18 microns wide at the septum. Microhair total length/width at septum 2.9. Microhair apical cells (15–)18–19.5(–21) microns long. Microhair apical cell/total length ratio 0.29–0.41. Stomata common; (21–)22.5–24(–27) microns long. Subsidiaries predominantly triangular. Intercostal short-cells common; not paired (mostly solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows (but the files often interrupted by longish short-cells). Costal silica bodies present in alternate cell files of the costal zones; almost exclusively saddle shaped (a rather rectangular version); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only. PCR sheath extensions absent. PCR cells without a suberised lamella. PCR cell chloroplasts with well developed grana; centripetal. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section; with the ribs more or less constant in size (round topped). Midrib conspicuous (via its marked abaxial keel, and the bulliform adaxial epidermis); with one bundle only. Bulliforms present in discrete, regular adaxial groups; associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries only); forming ‘figures’ (some forming I’s or ‘anchors’). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Cytology. Chromosome base number, x = 10. 2n = 30.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 1 species; Canada, U.S.A. to Argentina. Species of open habitats. Prairie.
Holarctic and Neotropical. Boreal and Madrean. Rocky Mountains. Pampas.
Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia schedonnardi.
Economic importance. Significant weed species: S. paniculatus.
References, etc. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • Abaxial epidermis of leaf blade
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).
