The grass genera of the world

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L. Watson and M. J. Dallwitz

Boissiera Hochst. & Steud.

Named for botanist Edmond Boissier.

Including Euraphis (Trin.) Lindley, Schnizleina Steud., Wiesta Boiss.

Sometimes referred to Bromus

Habit, vegetative morphology. Annual; caespitose (or the culms solitary). Culms 5–15 cm high; herbaceous. Culm nodes hairy. Culm internodes hollow. Leaves auriculate. Sheath margins joined. Leaf blades linear; narrow; 1–6 mm wide; flat; without cross venation; persistent. Ligule an unfringed membrane.

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

Inflorescence. Inflorescence paniculate; contracted; capitate, or more or less ovoid; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 15–30 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus present, or absent.

Glumes two; very unequal to more or less equal; shorter than the spikelets; (the longer) long relative to the adjacent lemmas; awnless; similar (hyaline). Lower glume 3 nerved. Upper glume 5 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets usually several; awned (reduced to a bunch of awns).

Female-fertile florets 2–5. Lemmas decidedly firmer than the glumes (papery to leathery); not becoming indurated; incised; irregularly 5–9 lobed (toothed); not deeply cleft; awned. Awns (5–)7(–9) (in a line across the lemma back); median and lateral; the median similar in form to the laterals; dorsal (from the upper part of the lemma back); from near the top; non-geniculate; straight to recurving; hairless (scabrid); about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein. The lateral awns shorter than the median to about equalling the median (inserted at the same level on the lemma back, the outer members shorter). Awn bases twisted. Lemmas hairy; non-carinate; 9–13 nerved; with the nerves confluent towards the tip, or with the nerves non-confluent. Palea present; relatively long; palea apex minutely dentate; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous. Stamens 3. Anthers 0.4–0.6 mm long. Ovary hairy; with a conspicuous apical appendage (the styles lateral). Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit medium sized; longitudinally grooved; compressed dorsiventrally. Hilum long-linear. Embryo small. Endosperm hard; without lipid; containing only simple starch grains. 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. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common; 30–39 microns long. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells common, or absent or very rare; not paired; not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous to horizontally-elongated smooth, or rounded (rather irregular), or crescentic.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Sclerenchyma all associated with vascular bundles.

Cytology. Chromosome base number, x = 7. 2n = 14 and 28. 2 and 4 ploid. Chromosomes ‘large’. Mean diploid 2c DNA value 3.7 pg.

Taxonomy. Pooideae; Triticodae; Bromeae.

Distribution, ecology, phytogeography. 1 species; western Asia. Mesophytic to xerophytic; species of open habitats. Dry stony soils.

Holarctic. Tethyan. Irano-Turanian.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia striiformis, Puccinia hordei, Puccinia recondita, and ‘Uromycesturcomanicum.

Economic importance. Important native pasture species: B. squarrosa.

References, etc. Leaf anatomical: this project.

Illustrations. • B. squarrosa: Fl. iraq, 1968

The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG).

Cite this publication as: ‘Watson, L., 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: 7th December 2015.’.