The grass genera of the world
Habit, vegetative morphology. Perennial; stoloniferous. Culms 5–15 cm high; herbaceous. Leaf blades linear; narrow; 2–3 mm wide; flat, or folded; exhibiting multicellular glands abaxially. The abaxial leaf blade glands on the blade margins. Leaf blades without cross venation; disarticulating from the sheaths (apparently). Ligule a fringed membrane to a fringe of hairs (a pubescent ridge).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.
Inflorescence. Inflorescence a single raceme (the raceme occasionally forked). Rachides flattened. Inflorescence espatheate (but the raceme usually partially enclosed in the uppermost, spathe-like sheath); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary (close or distant); secund (?); pedicellate.
Female-fertile spikelets. Spikelets more or less morphologically conventional (but the lemmas spirally arranged, forming an inverted cone, and changing form acropetally); 8 mm long; compressed dorsiventrally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Callus long (at the base of the lowermost floret); pointed.
Glumes two; (the upper) about equalling the spikelets (the lower shorter); (the upper) long relative to the adjacent lemmas; awnless; non-carinate; similar (membranous, persistent, amplexicaul at the base, the G2 larger). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets both distal and proximal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets with proximal incomplete florets. The proximal incomplete florets 2 (fan-shaped, embracing the fertile lemmas); epaleate; sterile. The proximal lemmas 4-lobed, the lobes acute to short-awned, inner lobes narrower, the lemma with a slender awn from middle of back; awned (dorsally, and mucronate or aristulate from the four lobes); 7–9 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas.
Female-fertile florets 2–3. Lemmas conspicuously non-distichous; similar to the proximal lemmas, becoming smaller acropetally; incised; 4 lobed (the outer lobes much longer); deeply cleft; awned. Awns 1; median; dorsal; from well down the back (from about middle); non-geniculate; hairless; much shorter than the body of the lemma. Lemmas hairy; non-carinate; 7–9 nerved. Palea present; relatively long (flat); entire to apically notched; awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; glabrous; not or scarcely vascularized. Stamens 3. Anthers short; not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit ellipsoid. Embryo with an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae not over-arching the stomata; commonly consisting of one oblique swelling per cell (sometimes cells with two). Mid-intercostal long-cells rectangular; having markedly sinuous walls (and outer walls pitted). Microhairs present; more or less spherical; clearly two-celled (the basal cell sunken); chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 6–9 microns long (but sunken). Microhair total length/width at septum 1.3. Microhair apical cell/total length ratio 0.6. Stomata common. Subsidiaries markedly triangular. Intercostal short-cells fairly common; in cork/silica-cell pairs and not paired (some solitary); silicified. Intercostal silica bodies absent to imperfectly developed; rounded (narrowly oval), or crescentic. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped (to rectangular); not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma; traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs (towards midrib), or adaxially flat (outside); with the ribs more or less constant in size (low). Midrib conspicuous; having a conventional arc of bundles (large median, several small strands either side). Bulliforms present in discrete, regular adaxial groups (including a large, median group in a groove over midrib); associated with colourless mesophyll cells to form deeply-penetrating fans (these linked to the abaxial epidermis by girders of colourless cells). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (nearly all bundles). Sclerenchyma forming a hypodermal plate adaxially in midrib.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage (Pommereulleae). Soreng et al. (2015): Chloridoideae; Cynodonteae; Eleusininae. 1 species (P. cornucopiae).
Distribution, phytogeography, ecology. Eastern Asia.
Species of open habitats.
References, etc. Leaf anatomical: Metcalfe 1960; Van den Borre 1994.
Special comments. Fruit data wanting. Illustrations. • P. cornucopiae: P. Beauv. (1812). • P. cornucopiae: Tangachariyar Kadambi, Hndb. S. Indian Grasses (1921)
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. delta-intkey.com/grass’.