Grass Genera of the World

L. Watson and M. J. Dallwitz


Apera Adans.

Perhaps from the Greek a (not) and peros (maimed), contrasting the well developed lemma awn with that of Calamagrostis calamagrostis, from which Adanson was distinguishing this genus.

Including Anemagrostis Trin.

Habit, vegetative morphology. Annual; caespitose. Culms 10–120 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 1–10 mm wide; not setaceous; flat, or rolled (convolute); without cross venation; persistent; an unfringed membrane; not truncate; 2–10 mm long.

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

Inflorescence. Inflorescence paniculate; open; with capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 2–3.6 mm long; compressed laterally; disarticulating above the glumes. Rachilla prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret; hairless; the rachilla extension when present, with incomplete florets. Hairy callus absent. Callus blunt.

Glumes two; very unequal (usually), or more or less equal (rarely); (the upper) long relative to the adjacent lemmas; pointed; awnless; non-carinate; similar (membranous). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.

Female-fertile florets 1 (usually), or 2–3. Lemmas bidentate; decidedly firmer than the glumes (firmly membranous); not becoming indurated (‘subindurate when mature’); incised; awned. Awns 1; median; dorsal; from near the top; non-geniculate, or geniculate (rarely); much longer than the body of the lemma; entered by one vein. Lemmas hairless; non-carinate; 5 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated (hyaline); 2-nerved; 2-keeled, or keel-less. Lodicules present; 2; free; membranous; glabrous; toothed. Stamens 3. Anthers 0.3–2 mm long; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; longitudinally grooved; compressed dorsiventrally. Hilum short. Embryo small; not waisted. 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.

Seedling with a tight coleoptile. First seedling leaf with a well-developed lamina. The lamina narrow; erect; 3 veined.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells fusiform; having markedly sinuous walls. Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare (very rare); in cork/silica-cell pairs (also solitaries); silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired (mainly solitary). Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Chromosomes ‘large’.

Taxonomy. Pooideae; Poodae; Aveneae.

Distribution, ecology, phytogeography. 3–4 species; Europe, western Asia. Commonly adventive. Mesophytic; species of open habitats. Dry sandy soils and arable land.

Holarctic and Antarctic. Boreal and Tethyan. Euro-Siberian. Mediterranean and Irano-Turanian. Patagonian. European and Siberian.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminis and Puccinia coronata. Smuts from Tilletiaceae. Tilletiaceae — Tilletia and Urocystis.

Economic importance. Significant weed species: A. interrupta, A. spica-venti.

References, etc. Leaf anatomical: this project.

Illustrations. • Abaxial epidermis of leaf blade. Apera spica-ventae.


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