Oxychloris Lazarides
From the Greek oxys (sharp), and the genus Chloris (from the Greek chloros) in which it was formerly included; referring to the long pungent callus which distinguishes it from Chloris.
Habit, vegetative morphology. Annual, or perennial (short-lived); caespitose. Culms 15–50 cm high; herbaceous; unbranched above (5–7 noded). Culm nodes glabrous. Culm internodes solid (spongy). Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades narrow (less than 3.5 mm wide); flat, or rolled; without abaxial multicellular glands; without cross venation; persistent; a fringed membrane (short). Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence of spicate main branches; digitate. Primary inflorescence branches 3–6. Rachides hollowed and flattened (triqetrous). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; secund (the rachis dorsiventral); biseriate; subsessile to pedicellate.
Female-fertile spikelets. Spikelets 1.8–4.5 mm long (-6); compressed laterally; disarticulating above the glumes (the glumes usually persistent); not disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (the sterile florets in a terminal cluster, separated from the basal floret by a thickened, elongated internode). Rachilla prolonged beyond the uppermost female-fertile floret (and modified with spongy tissue to form a conspicuous thickened internode, separating the clustered sterile florets from the basal fertile one); glabrous apart fom a few basal hairs; the rachilla extension with incomplete florets. Hairy callus present (2.5–3mm long, being elongated and pungent). Callus long; pointed.
Glumes two; very unequal; shorter than the spikelets; long relative to the adjacent lemmas; lateral to the rachis; hairless; glabrous; not pointed (G1 entire, G2 2-lobed or truncate); awnless; carinate; similar (thinly membranous to hyaline, often purple-tinged). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets (without paleas). The distal incomplete florets 3–5; clearly specialised and modified in form (the clustered sterile lemmas large, winged and awned, the lower ones broad, flaring and 7 nerved). Spikelets without proximal incomplete florets.
Female-fertile florets 1 (basal). Lemmas decidedly firmer than the glumes (cartilaginous to indurated); not becoming indurated (but dark brown when mature); incised; 2 lobed; not deeply cleft (2-toothed); awned. Awns 1; median; dorsal; from near the top; non-geniculate; hairless; about as long as the body of the lemma to much longer than the body of the lemma; entered by one vein. Lemmas hairy. The hairs in tufts (from near the apices of the lateral nerves and lower on the mid-nerve). Lemmas carinate (the mid-nerve ribbed); without a germination flap; 3 nerved (the laterals submarginal); with the nerves confluent towards the tip. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated (membranous); 2-nerved; 2-keeled. Palea keels winged (the wings ciliate). Lodicules absent. Stamens 3. Anthers very small; not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1.3–2 mm long); trigonous. Hilum short. Pericarp fused. Embryo large (almost as long as the fruit). Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell (mostly). Long-cells markedly different in shape costally and intercostally (the non-papillate costals narrower and more regular). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 22.5–24–27 microns long. Microhair basal cells 12 microns long. Microhairs 9.6–12–15 microns wide at the septum. Microhair total length/width at septum 1.8–2.5. Microhair apical cells (9–)10.5–12(–13.5) microns long. Microhair apical cell/total length ratio 0.33–0.56. Stomata common; 16.5–19.5 microns long. Subsidiaries dome-shaped and triangular. Intercostal short-cells common; not paired (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; exclusively saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; biochemical type NAD–ME (1 species); XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions present. Maximum number of extension cells 1. PCR cells without a suberised lamella. PCR cell chloroplasts elongated; with well developed grana; centripetal. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (seemingly, in the poor material seen). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Phytochemistry. Leaf blade chlorophyll a:b ratio 3.88–4.5.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 1 species; Australia. Xerophytic; species of open habitats; halophytic to glycophytic. Dry savanna.
Australian. North and East Australian and Central Australian. Tropical North and East Australian.
References, etc. Morphological/taxonomic: Lazarides 1985. Leaf anatomical: this project.
Illustrations. • Inflorescence, spikelet. • Spikelet. • Abaxial epidermis of leaf blade
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).
