Whiteochloa C.E. Hubb.
Habit, vegetative morphology. Annual (or short-lived perennials); caespitose to decumbent. Culms 30–105 cm high; herbaceous. Culm nodes hairy, or glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 2–5.5 mm wide; loosely folded, or flat; without cross venation; persistent; a fringed membrane.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (the branches solitary, usually distant); with capillary branchlets. Primary inflorescence branches inserted all around the main axis. Inflorescence with axes ending in spikelets (usually), or axes not ending in spikelets (the branches sometimes bristle-tipped in W. cymbiformis). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary, or paired; secund to not secund; pedicellate. Pedicel apices discoid (rarely), or cupuliform. Spikelets not in distinct ‘long-and-short’ combinations (but often paired).
Female-fertile spikelets. Spikelets 2.25–4 mm long; oblong, or elliptic, or obovate; slightly compressed laterally, or not noticeably compressed; falling with the glumes; with distinctly elongated rachilla internodes between the florets. The upper floret conspicuously stipitate (shortly so). Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal; (the upper) long relative to the adjacent lemmas; hairy (G2 hispid or ciliate on the nerves, with tubercle-based hairs), or hairless; awnless (sometimes mucronate); very dissimilar (membranous, the G1 broadly ovate and enclosing the base of the spikelet, the G2 larger, cymbiform, acuminate with a hardened apex). Lower glume 3–5 nerved. Upper glume 5–7 nerved (the nerves prominent). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male. The proximal lemmas awnless; 5 nerved; decidedly exceeding the female-fertile lemmas (with dorsal groove or depression); less firm than the female-fertile lemmas to similar in texture to the female-fertile lemmas (membranous to leathery); becoming indurated, or not becoming indurated.
Female-fertile florets 1. Lemmas decidedly firmer than the glumes; faintly but distinctly rugose; becoming indurated (crustaceous); yellow in fruit; entire; pointed (acute or acuminate); mucronate (with a slightly curved apiculum); hairy (apically puberulous), or hairless (glabrous); non-carinate; having the margins lying flat on the palea; 5 nerved. Palea present; relatively long; entire; awnless, without apical setae; indurated (with indurated flaps); 2-nerved; 2-keeled. Lodicules present; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit small (1.5–2.25 mm long); compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally (but the intercostals much larger, and inflated); of similar wall thickness costally and intercostally. Mid-intercostal long-cells fusiform; having markedly sinuous walls, or having straight or only gently undulating walls. Microhairs present; panicoid-type; 54–60 microns long; 6.3–9 microns wide at the septum. Microhair total length/width at septum 6.7–7.6. Microhair apical cells 36–39 microns long. Microhair apical cell/total length ratio 0.63–0.69. Stomata common; 33–36 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare; not paired (solitary); not silicified. Costal zones with short-cells. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS–. PCR sheath outlines uneven. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles; with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups, or not present in discrete, regular adaxial groups (then the epidermis irregularly bulliform); when clearly grouped, in simple fans (these large-celled, Zea-type). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. No Eriochloa-type ‘callus’.
Taxonomy. Panicoideae; Panicodae; Paniceae.
Distribution, ecology, phytogeography. 6 species; Australia and Moluccas. Species of open habitats. Sandy alluvial soils in savanna.
Australian. North and East Australian. Tropical North and East Australian.
References, etc. Leaf anatomical: this project.
Illustrations. • General aspect, spikelet. • Abaxial epidermis of leaf blade. • Transverse section 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).
