| # The grass genera of the world |

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

### Cortaderia Stapf

From the Argentine native name cortadera (cutting), alluding to the sharp edged leaf blades.

Type species: Type: C. selloana (Schult.) Asch. & Graeb.

Excluding Austroderia, Chimaerochloa, Moorea; cf. Chionochloa, Lamprothyrsus

Habit, vegetative morphology. Perennial; caespitose (mostly large, tussocky). Culms 100–400 cm high; branched above, or unbranched above (commonly). Culm nodes glabrous. Culm internodes hollow. Leaves mostly basal; non-auriculate. The sheaths disintegrating or rolling. Leaf blades linear (often harsh, with lacerating margins); with only the midrib prominent and sclerified, broad, or narrow; not pseudopetiolate; without cross venation; disarticulating from the sheaths, or persistent; once-folded in bud. Ligule present; a fringe of hairs. Contra-ligule present, or absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets, or dioecious (but sometimes virtually male-only); with hermaphrodite florets, or without hermaphrodite florets. The spikelets hermaphrodite, or female-only, or male-only (mainly gynodioecious, sometimes almost dioecious). Plants outbreeding and inbreeding. Apomictic (non-pseudogamous), or reproducing sexually.

Inflorescence. Inflorescence paniculate (large and plumose or small); open. Inflorescence with axes ending in spikelets. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 10–18 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus present. Callus long; pointed, or blunt.

Glumes two; more or less equal; shorter than the spikelets to about equalling the spikelets (from 2/3 as long); long relative to the adjacent lemmas; hairless; glabrous; pointed; awnless; carinate; similar (narrow, hyaline). Lower glume 1(–3) nerved. Upper glume 1(–3) nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 2–3(–6). Lemmas attenuate; similar in texture to the glumes to decidedly firmer than the glumes (membranous or hyaline); not becoming indurated; entire, or incised; when incised, 2 lobed (the lobes when present small, acute, with or without slight to well developed setae); not deeply cleft; awned, or awnless. Awns usually 1; median; from a sinus, or apical (then sometimes with basal setae representing lateral lobes); non-geniculate to geniculate; hairless; entered by several veins (3). Lemmas hairy. The hairs in tufts, or not in tufts; in transverse rows, or not in transverse rows. Lemmas non-carinate; 3 nerved. Palea present (glabrous or hairy); relatively long; entire (truncate); awnless, without apical setae (but hairy); not indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; fleshy; ciliate. Stamens 3, or 0 (in female plants of gynodioecious species). Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; brown.

Fruit, embryo and seedling. Fruit free from both lemma and palea. Hilum long-linear. Embryo large. Endosperm hard; without lipid; containing compound starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.

Ovule, embryology. Outer integument covering no more than the chalazal half of the ovule; more than two cells thick at the micropylar margin. Inner integument discontinuous distally; not thickened around the micropyle. Synergids haustorial (strongly developed); exhibiting large, globular starch grains.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally, or differing markedly in wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present, or absent; when present, panicoid-type. Stomata absent or very rare, or common. Subsidiaries dome-shaped, or parallel-sided and dome-shaped (C. bifida exhibiting a few parallels). Guard-cells when present, overlapped by the interstomatals (sic). Intercostal short-cells common; in cork/silica-cell pairs and not paired (solitary); when paired silicified. Intercostal silica bodies tall-and-narrow. Costal short-cells conspicuously in long rows and neither distinctly grouped into long rows nor predominantly paired (varying from vein to vein), or neither distinctly grouped into long rows nor predominantly paired (nearly all solitary in C. bifida, solitary and paired in C. selloana). Costal silica bodies variously horizontally-elongated crenate/sinuous, or tall-and-narrow, or ‘panicoid-type’; when panicoid type, mostly short dumb-bell shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section; with the ribs more or less constant in size (broad, flat-topped). Midrib conspicuous (very much so in C. selloana), or not readily distinguishable (C. archboldii); with one bundle only (C. archboldii), or having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups (at the bases of the furrows), or not present in discrete, regular adaxial groups (the groups then irregular or ill defined, of small cells); in simple fans (e.g. C. bifida, or more often the groups ill-defined and of small cells cf. Ammophila -e.g. C. selloana). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (in all the bundles). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups to in a continuous abaxial layer.

Culm anatomy. Culm internode bundles in three or more rings.

Phytochemistry. Leaves containing flavonoid sulphates (4 species), or without flavonoid sulphates (C. fulvida).

Special diagnostic feature. The median lemma awn not strongly flattened, laterals present or absent.

Cytology. Chromosome base number, x = 9. 2n = 36, 72, 90, and 108. 4, 8, 10, and 12 ploid. Chromosomes ‘small’.

Classification. Watson & Dallwitz (1994): Arundinoideae; Danthonieae. Soreng et al. (2015): Danthonioideae; Danthonieae. 24 species.

Distribution, phytogeography, ecology. South America.

Neotropical.

Commonly adventive. Mesophytic to xerophytic; species of open habitats. Hillsides, in scrub and in weedy places.

Economic aspects. Significant weed species: C. selloana, perhaps increasing in significance as such. Cultivated ornamentals, especially C. selloana.

Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Ustilago.

References, etc. Morphological/taxonomic: Zotov 1963. Leaf anatomical: Metcalfe 1960; studied by us - C. bifida, C. selloana.

Illustrations. • Cortaderia selloana: Gibbs Russell et al., 1990. • Ligule of Cortaderia selloana. • Cortaderia pilosa: Linder et al, Ann. Miss. Bot. Gard. 97 (2010). • Cortaderia bifida: Linder et al, Ann. Miss. Bot. Gard. 97 (2010). • Cortaderia jubata: Bot. Mag. 124 (1898). • Grass pollen antigens: Watson and Knox (1976). • Grass pollen antigens: cross-reactions against anti-Lolium serum. IMMUNOELECTROPHORESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Lolium perenne pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. Results are compared using raw extract (left) with those using boiled extract (right). Antigens allergenic in humans are concentrated in the heat-stable components. For experimental details and discussion of the taxonomic patterns among cross-reactions, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Lolium serum. IMMUNOELECTROPHRESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Lolium perenne pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. For experimental details and discussion of the taxonomic patterns among cross-reactios, see Watson and Knox (1976) and Watson (1983). • Heat stable grass pollen antigens (allergens): cross-reactions against anti-Lolium serum. IMMUNOELECTROPHRESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS-HEAT-STABLE COMPONENT).

Each slide with rabbit antiserum in the trough, boiled Lolium perenne pollen extract (control) in the upper well, and comparable boiled extracts from other genera in the lower wells, as indicated. For experimental details and discussion of the taxonomic patterns among cross-reactios, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Cynodon serum. IMMUNOELECTROPHORESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Cynodon dactylon pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. Results are compared using raw extract (left) with those using boiled extract (human allergens, right). For experimental details and discussion of the taxonomic patterns among cross-reactions, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Zea serum. IMMUNOELECTROPHORESIS OF GRASS POLLEN EXTRACTS (DIFFUSIBLE ANTIGENS).

Each slide with rabbit antiserum in the trough, Zea mays pollen extract (control) in the upper well, and comparable extracts from other genera in the lower wells, as indicated. Results are compared using raw extract (left) with those using boiled extract (where availabe, right). Antigens allergenic in humans are concentrated in the heat-stable components. For experimental details and discussion of the taxonomic patterns among cross-reactions, see Watson and Knox (1976) and Watson (1983). • Grass pollen antigens: cross-reactions against anti-Zea serum.

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: 15th June 2025. delta-intkey.com’.

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