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The grass genera of the world

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

Chionochloa Zotov

From the Greek chion (snow) and chloe (young green corn or grass), in reference to the common name of snowgrasses.

Snowgrasses, Wallaby grasses.

~ Danthonia sensu lato, Rytidosperma, cf. Cortaderia

Type species: Type: C. rigida (Raoul) Zotov.

Habit, vegetative morphology. Perennial; caespitose. Culms 20–250 cm high (usually in coarse tussocks invested below with old sheaths); herbaceous. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal, or intravaginal. Leaves mostly basal; non-auriculate. Sheaths with an apical hair tuft. Leaf blades linear; broad, or narrow; 0.8–10 mm wide (5–150cm long); setaceous, or not setaceous; flat, or rolled, or acicular; not pseudopetiolate; without cross venation; disarticulating from the sheaths (and sometimes fracturing into segments, cf. Cortaderia), or persistent. Ligule a fringe of hairs; usually about 1 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets, or dioecious (gynodioecious); with hermaphrodite florets, or without hermaphrodite florets. The spikelets hermaphrodite, or female-only; homomorphic. Plants inbreeding; chasmogamous.

Inflorescence. Inflorescence few spikeleted to many spikeleted; paniculate (usually hairy in the branch axils); open, or contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 6–18 mm long; pale, golden or purpled; compressed laterally; disarticulating above the glumes; with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret, or terminated by a female-fertile floret; the rachilla extension (when present) with incomplete florets. Hairy callus present (the long hairs covering the lower part of the lemma). Callus short; blunt.

Glumes two; very unequal to more or less equal; shorter than the spikelets to exceeding the spikelets (but usually shorter); shorter than the adjacent lemmas to long relative to the adjacent lemmas; hairless (glabrous, occasionally prickle-toothed), or hairy (the upper, sometimes long-hairy on the lower margin); pointed; awned (rarely), or awnless; similar (membranous, the margins thin). Lower glume 1(–3) nerved. Upper glume 3 nerved, or 5 nerved, or 7 nerved. Spikelets with female-fertile florets only, or with incomplete florets. The incomplete florets distal to the female-fertile florets. Spikelets without proximal incomplete florets.

Female-fertile florets 3–9. Lemmas not becoming indurated (membranous); incised; 2 lobed; deeply cleft to not deeply cleft (the lateral lobes usually shorter than th body); awned. Awns 1, or 3; median, or median and lateral (the lobes usually short-awned); the median different in form from the laterals (when laterals present); from a sinus; geniculate; entered by several veins (3 in C. antarctica). The lateral awns shorter than the median. Awn bases twisted, or not twisted; flattened. Lemmas hairy (on the margins, or all over). The hairs not in tufts; not in transverse rows (in vertical lines between the veins). Lemmas non-carinate; 7–9 nerved. Palea present (hairy on the flanks below); relatively long (exceeding the lemma sinus); usually apically notched; awnless, without apical setae (usually), or awned (the keels being produced into 2mm awns in C. beddiei); 2-nerved; 2-keeled. Palea back glabrous, or scabrous, or hairy. Palea keels hairy. Lodicules present; 2; free; fleshy; ciliate, or glabrous (? - according to Hooker’s Fl. Antarctica illustration of his Bromus antacticus, nowadays referred to C. antarctica); toothed. Stamens 3, or 0. Anthers (2–)4–5(–6) mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit small ((1.5-)2.5–3.5(-4) mm long); obovate, rugulose or smooth; longitudinally grooved. Hilum long-linear (1/2 to 2/3 the length of the caryopsis). Embryo large (1/3 to 1/2 the caryopsis length). Endosperm containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode.

Ovule, embryology. Outer integument covering no more than the chalazal half of the ovule. Inner integument discontinuous distally. Synergids haustorial.

Abaxial leaf blade epidermis. Costal/intercostal zonation lacking. Papillae absent (but present adaxially). Long-cells similar in shape costally and intercostally (the intercostal zones being indistinguishable); of similar wall thickness costally and intercostally (thick to very thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent (but sometimes present adaxially). Stomata absent or very rare (sometimes very rare); 30–43 microns long. Subsidiaries dome-shaped, or dome-shaped to triangular. Intercostal short-cells common; in cork/silica-cell pairs, or not paired; silicified, or not silicified. Costal short-cells predominantly paired, or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies rounded, or saddle shaped, or tall-and-narrow, or crescentic, or ‘panicoid-type’.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size, or with the ribs very irregular in sizes (mostly). Midrib conspicuous, or not readily distinguishable; with one bundle only; with colourless mesophyll adaxially, or without colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups (at the bases of the furrows, the groups sometimes small); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’, or nowhere forming ‘figures’. Sclerenchyma not all bundle-associated (C. conspicua, C. frigida). The ‘extra’ sclerenchyma in abaxial groups to in a continuous abaxial layer.

Phytochemistry. Leaves containing flavonoid sulphates (C. conspicua, C. frigida).

Cytology. Chromosome base number, x = 6. 2n = 42, 48, 72, and 96. 6, 12, and 16 ploid.

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 23 species.

Distribution, phytogeography, ecology. New Zealand, southeastern Australia.

Rusts and smuts. Rusts — Puccinia.

References, etc. Morphological/taxonomic: Zotov 1963; Vickery 1956; Connor 1991. Leaf anatomical: studied by us (from Australian material only) - C. conspicua (Forst.) Zotov, C. frigida (Vickery) Conert, C. pallida (R. Br.) Conert; Metcalfe’s (1960) descriptions of 8 New Zealand spp. are less detailed than usual.

Special comments. Sexuality of the plants is regularly described and qualified using the same ambiguous wording in all the descriptions seen; viz., "gynodioecious ("male", in this context, indicating the bisexual state". It is unclear what this means.). Illustrations. • cf. C. antarctica (as Bromus): Hooker, Fl. Antarctica (1844). • Chionochloa rigida (as Danthonia): Hooker, Fl. Novae-Zelandiae (1853). • Chionochloa bromoides (as Danthonia): Hooker, Fl. Novae-Zelandiae (1853). • C. conspicua, abaxial epidermis of leaf blade: this project. • C. conspicua, TS leaf blade: this project. • C. cunninghamii, abaxial epidermis of leaf blade: this project. • C. frigida, 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.’.