The grass genera of the world
Including Gynerium Humb. & Bonpl.
Habit, vegetative morphology. Very large, soil-binding, perennial; reedy; rhizomatous. Culms 200–1000 cm high. Culm internodes solid. Leaves not basally aggregated (clustered towards the culm tips); non-auriculate; without auricular setae (but with tufts of longer hairs at the auricle positions). Leaf blades linear-lanceolate to lanceolate; broad; 4–8 mm wide (and to 2 m long, sharply serrulate); flat; without cross venation; disarticulating from the sheaths (so that the still-laminate leaves forming large flabelliform crowns on the culms). Ligule a fringed membrane to a fringe of hairs; to 4mm long. Contra-ligule present (a membrane), or absent.
Reproductive organization. Plants dioecious; without hermaphrodite florets. The spikelets all alike in sexuality (on the same plant); female-only, or male-only. Plants outbreeding.
Inflorescence. Inflorescence paniculate (very large); open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.
Female-sterile spikelets. Male spikelets with glabrous lemmas, short paleas, fleshy lodicules and two stamens. Male florets 2 staminate.
Female-fertile spikelets. Spikelets 6–9 mm long (approximately 8 mm); compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless; the rachilla extension naked. Hairy callus present. Callus short.
Glumes two; very unequal; (the upper) long relative to the adjacent lemmas (exceeding them); hairless; pointed; awnless (but long attenuate), or awned; carinate (G1), or non-carinate (G2 rounded on the back); very dissimilar (the lower hyaline, the upper acuminate-subulate and recurved). Lower glume about 0.3 times the length of the upper glume; 1 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.
Female-fertile florets 2. Lemmas similar in texture to the glumes; not becoming indurated; entire; pointed; awnless (but long-attenuate, the tip with long villous hairs); silky hairy; non-carinate (but keeled above); 5 nerved. Palea present; relatively long; apically notched; awnless, without apical setae; not indurated; 2-nerved; 2-keeled (and ciliate). Lodicules present; 2; free; membranous (poorly developed); ciliate; not toothed. Stamens 0 (2 staminodes). Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous (but impossible to distinguish between costal and astomatal intercostal regions). Papillae absent. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type (at least adaxially - the abaxial ones mostly damaged in material seen). Stomata common; 33–39 microns long. Subsidiaries dome-shaped (but becoming somewhat triangular at lower levels of focus). Guard-cells overlapping to flush with the interstomatals. Costal short-cells predominantly paired. Costal silica bodies rounded, saddle shaped, and crescentic.
Transverse section of leaf blade, physiology. C3; XyMS+ (the mestome sheath often several cells thick, heavily lignified). Mesophyll with non-radiate chlorenchyma; without adaxial palisade; traversed by columns of colourless mesophyll cells (these very broad, extending from the adaxial bulliforms to join with conspicuous abaxial sclerenchyma columns, rather than extending from epidermis to epidermis); with arm cells (very conspicuous). Leaf blade with distinct, prominent adaxial ribs (the ribs low and broad). Midrib conspicuous (large, with a wide abaxial keel and big air spaces between the major vascular bundles); having complex vascularization (comprising an arc of several large primary bundles situated towards the adaxial surface, and an abaxial arc of numerous minor bundles some of which occur in the abaxial sclerenchyma girders of the primaries); with colourless mesophyll adaxially. The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (in each furrow); associated with colourless mesophyll cells to form deeply-penetrating fans (these linked with the traversing colourless columns). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles, save some in the midrib); forming figures (most bundles with very tall, narrow Is). Sclerenchyma not all bundle-associated. The extra sclerenchyma in abaxial groups and in adaxial groups; abaxial-hypodermal, the groups continuous with colourless columns and adaxial-hypodermal, contiguous with the bulliforms (there being conspicuous intercostal abaxial girders linked with the colourless columns, which constitute false costae in the abaxial epidermis, and some adaxial groups lining the sides of the bulliforms).
Phytochemistry. Leaves containing flavonoid sulphates (G. sagittatum).
Cytology. 2n = 72 and 76.
Classification. Watson & Dallwitz (1994): Arundinoideae; Arundineae. Soreng et al. (2015): Panicoideae; Gynerieae. 1 species (G. sagittatum).
Distribution, phytogeography, ecology. Mexico to subtropical South America.
Helophytic (streamsides and wet places).
Economic aspects. Used for construction work, basketry etc.
References, etc. Leaf anatomical: Metcalfe 1960, and studied by us.
Special comments. Fruit data wanting. Illustrations. • G. sagittatum: Nicora & Rúgolo de Agrasar (1987). • G. sagittatum: 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: 11th December 2017. delta-intkey.com/grass’.