Grass Genera of the World

L. Watson and M. J. Dallwitz


Scribneria Hackel

Named for F. Lamson-Scribner.

Habit, vegetative morphology. Annual; caespitose. Culms 7–30 cm high; herbaceous; unbranched above. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; about 0.8–1.6 mm wide; almost filiform; rolled (involute); without cross venation; persistent; an unfringed membrane; not truncate (acuminate, becoming lacerate); 1.5–4 mm long. Contra-ligule absent.

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

Inflorescence. Inflorescence a single spike (slender), or a single raceme (with short pedicels), or paniculate (rarely, having two spikelets per node, on different pedicels or on one branched peduncle); contracted; spicate. Rachides hollowed. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary (mostly), or paired (occasionally); not secund; distichous; subsessile to pedicellate (the pedicels embedded with the spikelets the rachis hollows, becoming shorter towards the inflorescence tip); imbricate.

Female-fertile spikelets. Spikelets 4–7 mm long; compressed laterally (flatwise against the axis); disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret; hairy; the rachilla extension naked. Hairy callus present. Callus short (oblique).

Glumes two; more or less equal; exceeding the spikelets; long relative to the adjacent lemmas (exceeding them); free; lateral to the rachis; hairless; glabrous (minutely scabrous on the nerves); pointed; awnless; non-carinate (but keeled on the outer nerves); similar (usually purplish-tinged, both strongly keeled on the outer nerve with the side adjoining the rachis nerveless, one - assumed to be the G1 - markedly narrower). Lower glume two-keeled (G2 also); 2 nerved. Upper glume 4 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas less firm than the glumes (membranous); not becoming indurated; incised; 2 lobed; not deeply cleft (shortly bifid); awned. Awns 1; median; from a sinus; non-geniculate; hairless; much shorter than the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairless; glabrous; carinate; without a germination flap; 3–5 nerved. Palea present; relatively long; tightly clasped by the lemma; briefly apically notched; awnless, without apical setae; thinner than the lemma (hyaline, glabrous); not indurated; 2-nerved; keel-less (the nerves closely apposed). Lodicules present; 2; free; membranous; glabrous; not toothed; not or scarcely vascularized. Stamens 1. Ovary glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (2.5 mm long); fusiform; not noticeably compressed. Hilum short (punctiform). Embryo small (but fairly large for a pooid grass - about 1/4 of the grain length). Endosperm hard; with lipid; containing compound starch grains.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular; having straight or only gently undulating walls. Microhairs absent. Stomata common; (31–)34–38(–39) microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals (slightly). Intercostal short-cells absent or very rare. Costal short-cells predominantly paired. Costal silica bodies absent (in material seen), or present and well developed; when present, horizontally-elongated smooth, or rounded.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with slight, rounded adaxial ribs; with the ribs more or less constant in size. Midrib conspicuous (by its association with a small abaxial keel, and by the bundle possessing an abaxial strand rather than a girder); with one bundle only. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the main bundles with I’s). Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 13.

Taxonomy. Pooideae; Poodae; Aveneae.

Distribution, ecology, phytogeography. 1 species; western U.S.A.

Holarctic. Madrean.

Rusts and smuts. Rusts — Puccinia.

References, etc. Leaf anatomical: this project.


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).

Index