The grass genera of the world

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

Triniochloa A. Hitchc.

Habit, vegetative morphology. Perennial; caespitose. Culms herbaceous. Leaves non-auriculate. Sheath margins joined. Leaf blades without cross venation. Ligule an unfringed membrane; not truncate; 8–9 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence paniculate; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 10–12 mm long; not noticeably compressed, or compressed dorsiventrally; disarticulating above the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present. Callus blunt.

Glumes present; two; relatively large; very unequal; shorter than the spikelets, or about equalling the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; pointed (acute or acuminate); awnless; non-carinate; similar (thin, membranous, papery). Lower glume 1 nerved. Upper glume 1 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (subleathery); not becoming indurated; incised; setaceously 2 lobed; not deeply cleft; awned. Awns 1; median; dorsal; from near the top, or from well down the back; geniculate; entered by several veins. Lemmas hairless; non-carinate; without a germination flap; 5(–7) nerved. Palea present; relatively long; 2-nerved; closely 2-keeled (sulcate between). Lodicules present; 2; joined; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit medium sized (about 5 mm long); compressed dorsiventrally. Hilum long-linear. Embryo small. Endosperm hard. Embryo with an epiblast.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular and fusiform; having markedly sinuous walls and having straight or only gently undulating walls. Microhairs absent. Stomata absent or very rare. Intercostal short-cells common; not paired (nearly all solitary); not silicified. A few prickles present over the veins. Costal zones with short-cells. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous and ‘panicoid-type’ (a continuous series of elongated-crenate, elongated-nodular and crosses, even a few dumb-bells); when panicoid type, cross shaped, or dumb-bell shaped, or nodular; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with the ribs very irregular in sizes. Midrib conspicuous (via its large bundle and a prominent abaxial keel); with one bundle only. The lamina symmetrical on either side of the midrib. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming ‘figures’ (the large bundles with T’s, the smaller bundles with I’s). Sclerenchyma all associated with vascular bundles.

Special diagnostic feature. The upper part of the lemma without pappus-like hairs.

Cytology. Chromosome base number, x = 8. 2n = 32. 4 ploid.

Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Meliceae. Soreng et al. (2015): Pooideae; Meliceae. 4–5 species.

Distribution, phytogeography, ecology. Mexico to Ecuador and Peru.

Xerophytic; species of open habitats. Stony hillsides.

References, etc. Leaf anatomical: studied by us - T. stipoides (H.B.K.) Hitchcock.

Illustrations. • T. stipoides: Swallen (1955), Fl. of Guatemsla II. • T. stipoides, 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.’.