The grass genera of the world
Including Arrozia Kunth, Caryochloa Trin.
Habit, vegetative morphology. Annual, or perennial; stoloniferous, or decumbent. The flowering culms leafy. Culms 10–30 cm high; herbaceous; sometimes amply branched above. Plants unarmed. Leaves not basally aggregated; without auricular setae. Leaf blades broad, or narrow; 1–10(–20) mm wide; flat; not pseudopetiolate. Ligule an unfringed membrane; not truncate (obtuse or acuminate, entire or laciniate); long.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets in different inflorescences (the staminate and pistillate spikelets in separate panicles), or on different branches of the same inflorescence (then with the male spikelets uppermost).
Inflorescence. Inflorescence paniculate (the panicles terminal and axillary); with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary (at least, not paired); not secund; pedicellate.
Female-sterile spikelets. Male spikelets with one floret, a pointed lemma and 6–18 stamens. The male spikelets without glumes; 1 floreted. The lemmas awnless. Male florets 6–18 staminate.
Female-fertile spikelets. Spikelets unconventional (assumed to lack glumes); 2–5 mm long; suborbicular, or oblong, or elliptic, or lanceolate, or obovate; compressed laterally to not noticeably compressed; disarticulating from the pedicel. Rachilla terminated by a female-fertile floret.
Glumes absent. Spikelets with female-fertile florets only.
Female-fertile florets 1. Lemmas not becoming indurated (thin); entire; pointed; awnless, or mucronate (?); lemmas several to many nerved. Palea present; relatively long (about equalling the lemma); thinner than the lemma (thin); not indurated; several nerved; one-keeled. Stamens 0. Ovary apically glabrous. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (1–2 mm long); ellipsoid to subglobose; not noticeably compressed. Hilum long-linear. Pericarp thick and hard; free. Embryo small. Endosperm hard; without lipid.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae not over-arching the stomata; several per cell (or rather, many, on all cells save the guard-cells and subsidiaries). Long-cells markedly different in shape costally and intercostally (the costals narrower, more regularly rectangular); of similar wall thickness costally and intercostally (thin walled). Intercostal zones with typical long-cells to exhibiting many atypical long-cells. Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls (the sinuosity fairly coarse). Microhairs present; elongated; ostensibly one-celled (cf. those of Hygroryza); minute; 19.5–21 microns long. Stomata common; 27–30 microns long. Subsidiaries non-papillate; triangular (a few), or dome-shaped (mostly). Guard-cells overlapped by the interstomatals (very slightly). Intercostal short-cells common; not paired (mostly seemingly solitary); silicified. Intercostal silica bodies oryzoid-type. Large prickle bases common. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies panicoid-type (predominating), or oryzoid (a few, especially alongside the veins); when panicoid type, short dumb-bell shaped, or cross shaped (the latter sometimes intergrading with oryzoid type); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; with arm cells (seemingly, but not very conspicuous in the material seen); without fusoids. Midrib conspicuous (by a keel, and a large lacuna or region of colourless tissue above); having a conventional arc of bundles (a large median, with two smaller bundles on either side); with colourless mesophyll adaxially (probably). Bulliforms not present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Oryzeae. Soreng et al. (2015): Oryzoideae; Oryzeae; Zizaniinae. 11 species.
Distribution, phytogeography, ecology. Southern U.S.A. to tropical South America.
Hydrophytic, or helophytic.
Economic aspects. Significant weed species: L. spruceana (in North America).
References, etc. Leaf anatomical: this project.
Illustrations. • L. peruviana, and L. fluitans as Hydrochloa caroliniensis: P. Beauv. (1812). • L. peruviana: 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’.