Grass Genera of the World

L. Watson and M. J. Dallwitz


Halopyrum Stapf

Habit, vegetative morphology. Perennial; stoloniferous and caespitose. Culms herbaceous (tough). Leaves non-auriculate. Leaf blades narrow (junciform); rolled (convolute, stiff, filiform-tipped); not needle-like; without abaxial multicellular glands; without cross venation; disarticulating from the sheaths; a fringe of hairs.

Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets; without hidden cleistogenes.

Inflorescence. Inflorescence of spicate main branches (the short, erect branches being themselves unbranched), or paniculate (elongated, contracted); non-digitate; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund.

Female-fertile spikelets. Spikelets 10–30 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (the internodes bearded at the tip, with long hairs up to half the lemma length); the rachilla extension with incomplete florets. Hairy callus present.

Glumes two; more or less equal (subequal); shorter than the spikelets; shorter than the adjacent lemmas to long relative to the adjacent lemmas; hairless; pointed (acuminate); awnless; carinate; similar (leathery, ovate-lanceolate). Lower glume shorter than the lowest lemma to about equalling the lowest lemma; 3–5 nerved. Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.

Female-fertile florets 6–20. Lemmas ovate-oblong, acute; similar in texture to the glumes (leathery); entire, or incised; pointed; if incised 2 lobed; not deeply cleft (bidenticulate); mucronate; hairy (asperulous or minutely hairy); carinate; 3 nerved. Palea present; relatively long; entire; awnless, without apical setae; 2-nerved; 2-keeled (the keels scaberulous). Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Ovary glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit ellipsoid; longitudinally grooved; compressed dorsiventrally (concavo-convex). 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 (in the deep grooves, and abundant adaxially); intercostal. Intercostal papillae over-arching the stomata; consisting of one oblique swelling per cell, or consisting of one symmetrical projection per cell (finger-like). Long-cells differing markedly in wall thickness costally and intercostally (the costals thick-walled). Microhairs present (in deep intercostal grooves); more or less spherical; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 27–33–34.5 microns long; 21–22.5 microns wide at the septum. Microhair total length/width at septum 1.2–1.6. Microhair apical cells 17.4–27 microns long. Microhair apical cell/total length ratio 0.54–0.78. Stomata absent or very rare. Intercostal silica bodies absent. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies present throughout the costal zones; saddle shaped (mainly), or tall-and-narrow, or ‘panicoid-type’ (a few).

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 present. Maximum number of extension cells 1–5. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade ‘nodular’ in section; with the ribs very irregular in sizes. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans and associated with colourless mesophyll cells to form deeply-penetrating fans (sometimes linked with traversing columns of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.

Taxonomy. Chloridoideae; main chloridoid assemblage.

Distribution, ecology, phytogeography. 1 species; coastal Indian Ocean. Xerophytic; species of open habitats; halophytic. A coastal sand stabilizer.

Holarctic and Paleotropical. Tethyan. African, Madagascan, and Indomalesian. Irano-Turanian. Saharo-Sindian and Sudano-Angolan. Indian. Sahelo-Sudanian, Somalo-Ethiopian, and South Tropical African.

References, etc. Morphological/taxonomic: Stapf 1896. 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