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The grass genera of the world

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

Piptochaetium Presl

From the Greek piptein (to fall) and chaite (bristle), alluding to deciduous awns.

Type species: Type: P. montevidense (Spreng.) Parodi.

Including Caryochloa Spreng., Podopogon Raf.

Habit, vegetative morphology. Perennial; caespitose. Culms 30–150 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves mostly basal; non-auriculate (but with thickenings at the auricle positions). Leaf blades broad, or narrow (narrow, usually involute); without cross venation; persistent. Ligule an unfringed membrane; 0.3–3(–8) mm long. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.

Inflorescence. Inflorescence few spikeleted to many spikeleted; paniculate; open (usually), or contracted; with capillary branchlets, or without capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; usually long pedicellate.

Female-fertile spikelets. Spikelets 2–24 mm long; compressed laterally to not noticeably compressed; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus usually present. The callus hairs brown. Callus short; acute.

Glumes two; more or less equal; about equalling the spikelets, or exceeding the spikelets; long relative to the adjacent lemmas (usually exceeding the floret); hairless; pointed (abruptly acuminate); awnless; non-carinate (convex on the back); similar (thin). Lower glume 3–7 nerved. Upper glume 3–7 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.

Female-fertile florets 1. Lemmas often dark-pigmented, sometimes cylindrical, usually asymmetrically obovoid to subglobose or lenticular; not convolute (the margins involute, fitting into the paleal groove); saccate (usually), or not saccate; with an apical ‘crown’; decidedly firmer than the glumes; becoming indurated (smooth, verrucose, striate or tuberculate, the epidermis without silica bodies); awned. Awns 1; median; apical (the summit of the lemma often expanded into a corona); geniculate (often bi-geniculate), or geniculate; sometimes non-geniculate and curved; hairless (glabrous), or hairy; much longer than the body of the lemma, or much shorter than the body of the lemma (much reduced, in P. cucullatum); deciduous, or persistent. Lemmas hairy, or hairless; carinate (usually somewhat compressed and keeled); having the margins inrolled against the palea; without a germination flap; 5 nerved. Palea present; relatively long (the apex of the keel projecting as a minute point above the summit of the lemma); prow-tipped; entire; pointed, sometimes with an apical mucro; indurated (except marginally); 2-nerved (these fairly adjacent); 2-keeled (with a narrow sulcus between the two close indurated keels, which are not enclosed by the lemma). Lodicules present; 2, or 3; free; membranous; glabrous; not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit longitudinally grooved. Hilum long-linear. Endosperm hard; without lipid.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular, or rectangular and fusiform; having markedly sinuous walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies tall-and-narrow, or crescentic, or cross-shaped. Small prickles abundant. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll traversed by columns of colourless mesophyll cells (at the ‘hinge positions’). Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section (having only 3 similar sized veins, the lamina very thin and lacking photosynthetic tissue between the 3 ‘ribs’). Midrib with one bundle only. Bulliforms present in discrete, regular adaxial groups (the groups broad, at the bases of the furrows). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent (combining adaxial and abaxial strands, or adaxial strands and abaxial girders). Sclerenchyma not all bundle-associated. The ‘extra’ sclerenchyma in abaxial groups; abaxial-hypodermal, the groups continuous with colourless columns.

Cytology. Chromosome base number, x = 11, or 12 (?). 2n = 22 and 44. 2 and 4 ploid.

Classification. Watson & Dallwitz (1994): Stipoideae; Stipeae. Soreng et al. (2015): Pooideae; Stipeae. About 30 species.

Distribution, phytogeography, ecology. North & (mainly) South America.

Mesophytic to xerophytic; species of open habitats. Steppe.

Economic aspects. Important native pasture species: P. fimbriatum.

Rusts and smuts. Rusts — Puccinia. Taxonomically wide-ranging species: Puccinia graminella. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae — Tilletia. Ustilaginaceae — Ustilago.

References, etc. Leaf anatomical: Metcalfe 1960; studied by us - P. brevicalyx Ricker ex Hitchc., P. fimbriatum (H.B.K.) Hitchc.

Illustrations. • P. leiopodum: Nicora & Rúgolo de Agrasar (1987). • P. fimbriatum, as Stipa: Kunth (1835). • P. fimbriatum, abaxial epidermis of 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.’.