The grass genera of the world
Including Monostemon Henr.
Habit, vegetative morphology. Perennial; caespitose. Culms 40–80 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate; without auricular setae. Sheaths glabrous or pilose, becoming fibrous when dead. Leaf blades linear; narrow; flat; not pseudopetiolate; without cross venation; persistent (the fibrous remains of the sheaths persisting). Ligule an unfringed membrane; truncate; 1–3 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; exposed-cleistogamous, or chasmogamous.
Inflorescence. Inflorescence paniculate; open (the spikelets clustered at the extremities); with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate; imbricate.
Female-fertile spikelets. Spikelets 1.2–2.5 mm long; compressed laterally (the individual florets dorsiventrally compressed); disarticulating above the glumes; not disarticulating between the florets (at least, the florets tending to fall together); with conventional internode spacings. Rachilla prolonged beyond the uppermost female-fertile floret. Hairy callus absent.
Glumes two; more or less equal; about equalling the spikelets; long relative to the adjacent lemmas; hairless; scabrous (to echinulate); awnless; carinate to non-carinate; similar (broadly lanceolate-navicular). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only, or with incomplete florets (the presence of a distal rudiment variable). The incomplete florets (when present) distal to the female-fertile florets. The distal incomplete florets when present, merely underdeveloped; awnless.
Female-fertile florets 2–3. Lemmas navicular, dorsally gibbous but without the Briza umbo, the margins infolded on the palea; similar in texture to the glumes; not becoming indurated (leathery); entire; pointed to blunt; awnless to mucronate; hairless; verrucose to echinulate; non-carinate; without a germination flap; 5 nerved. Palea present; relatively long; tightly clasped by the lemma; entire (lanceolate, acute); awnless, without apical setae; textured like the lemma (leathery); not indurated; 2-nerved; 2-keeled (and flat between the keels). Palea keels wingless; glabrous to scabrous. Lodicules present; 2; free; membranous; glabrous; not toothed (lanceolate). Stamens 1. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea (adhering to the palea along the two lateral grooves); small; ellipsoid; with two lateral, longitudinal grooves, wherein lie the margins of the palea; compressed dorsiventrally (ventrally flattened, dorsally convex). Hilum short. Embryo small. Endosperm hard.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower, rectangular). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata fairly common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells conspicuously in long rows (the long rows interrupted only occasionally, by prickles). Costal silica bodies horizontally-elongated crenate/sinuous, or panicoid-type (the bodies ill defined, in the material seen); if panicoid type, nodular; not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Leaf blade with distinct, prominent adaxial ribs, or nodular in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in all the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures (in all the main bundles). Sclerenchyma all associated with vascular bundles.
Special diagnostic feature. Lemmas not as in Briza (q.v.). Female-fertile lemma not as in Lombardochloa (q.v.).
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Calothecinae. 2 species.
Distribution, phytogeography, ecology. South America.
References, etc. Leaf anatomical: this project.
Illustrations. • M. poimorpha: Nicora & Rúgolo de Agrasar (1987)
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: 13th November 2017. delta-intkey.com/grass’.