The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Whiteochloa C.E. Hubb.

Type species: Type: W. semitonsa (F.Muell. ex Benth.) 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 leaf sheaths rounded. 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. Ligule a fringed membrane.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.

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 apically 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.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae; Cenchrinae. 6 species.

Distribution, phytogeography, ecology. Australia and Moluccas.

Species of open habitats. Sandy alluvial soils in savanna.

References, etc. Leaf anatomical: studied by us - W. cymbiformis (Hughes) B.K. Simon, W. semitonsa (Muell. ex Benth.) Hubbard.

Illustrations. • W. airoides: Gardner, 1952. • W. cymbiformis, abaxial epidermis of leaf blade: this project. • W. cymbiformis, TS leaf blade: this project

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or 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, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., 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: 11th December 2017.’.