Orinus A. Hitchc.
From the Greek oreinos (a mountaineer), alluding to habitat.
Habit, vegetative morphology. Perennial; rhizomatous and caespitose. Culms 30–50 cm high; herbaceous. Rhizomes pachymorph. Plants unarmed. Leaves non-auriculate; without auricular setae. Leaf blades narrow; 2–5 mm wide (by 3–10 cm long, sparsely pilose); becoming involute; with setiform, slightly pungent tips; exhibiting multicellular glands abaxially. The abaxial leaf blade glands intercostal. Leaf blades without cross venation; thin, lacerate; 1 mm long.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality. Plants without hidden cleistogenes.
Inflorescence. Inflorescence of spicate main branches (erect or ascending racemes); non-digitate (the axis elongate). Primary inflorescence branches 5–8. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (the rachides dorsiventral); not two-ranked (in one row, on one side of the rachis, appressed); shortly pedicellate.
Female-fertile spikelets. Spikelets 6 mm long; pale or leaden-purplish tinged; disarticulating above the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (a 1 mm internode between the first and second florets). Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous).
Glumes two; relatively large (4–5 mm long); more or less equal (only slightly unequal); shorter than the adjacent lemmas; hairy (sparsely villous to nearly glabrous); without conspicuous tufts or rows of hairs; pointed (acute); awnless; similar (pale, membranous). Lower glume shorter than the lowest lemma; 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. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 2–3 (-4). Lemmas similar in texture to the glumes (the tips hyaline); not becoming indurated; entire; blunt, or pointed; awnless, or mucronate (but only slightly so); hairy (with villous hairs all over, not confined to the nerves as in Leptochloa and Trichoneura); indistinctly carinate; 3 nerved (somewhat concave between the nerves). Palea present; relatively long; awnless, without apical setae; 2-keeled. Palea keels hairy. Stamens 3; with free filaments. Anthers 2.5–2.75 mm long. Stigmas 2.
Fruit, embryo and seedling. Fruit small (2.5 mm long); not noticeably compressed (cylindrical). Hilum short. Pericarp fused. Embryo large (about 1/3 the grain length).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present (very abundant); costal and intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell. Intercostal zones with typical long-cells (or these rather short). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 21–24–25.5 microns long. Microhair basal cells 24 microns long. Microhairs (9.3–)10.5–11.4(–15) microns wide at the septum. Microhair total length/width at septum 1.6–2.6. Microhair apical cells 10.5–12–16.5 microns long. Microhair apical cell/total length ratio 0.41–0.68. Stomata common (alongside the veins); 21–22.5(–25.5) microns long. Subsidiaries triangular (though not readily observable). Intercostal short-cells common; in cork/silica-cell pairs and not paired (some solitary); not silicified. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; ‘panicoid-type’; limited to cross shaped and butterfly shaped; 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. Leaf blade ‘nodular’ in section to adaxially flat. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (these predominating, with large, deeply penetrating median cells), or associated with colourless mesophyll cells to form deeply-penetrating fans (a few). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (all bundles with small I’s). Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 2 species; Western Himalayas. Xerophytic; species of open habitats. Desert sand dunes at high altitude.
Holarctic. Tethyan. Irano-Turanian.
References, etc. Morphological/taxonomic: Hitchcock 1933. Leaf anatomical: this project.
Illustrations. • Abaxial epidermis of leaf blade. • Leaf blade transverse section
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).
