Tricholaena Schrad.
From the Greek thrix, trichos (a hair) and chlaena (mantle), referring to silky spikelets.
Excluding Rhynchelytrum
Habit, vegetative morphology. Annual (rarely), or perennial; caespitose, or decumbent. Culms 10–120 cm high; herbaceous; unbranched above. Culm internodes hollow. Leaf blades often glaucous-inrolled, rigid; without cross venation; a fringed membrane (very narrow), or a fringe of hairs.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. Apomictic, or reproducing sexually.
Inflorescence. Inflorescence paniculate; open, or contracted; with capillary branchlets (these flexuous); espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 2–3.5 mm long; compressed laterally; with a distinctly elongated rachilla internode between the glumes (having G1 slightly separated from G2). Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes present; one per spikelet, or two; very unequal; (the longer) long relative to the adjacent lemmas; free; hairy (the upper and/or both sometimes variously hairy), or hairless; awnless (the upper sometimes mucronate); very dissimilar (the lower often reduced to a tiny scale, hairy or glabrous), or similar (rarely). Lower glume about 0.1–0.2 times the length of the upper glume; 0–1 nerved. Upper glume indistinctly 3 nerved, or 5 nerved (thinly membranous, emarginate to acute). Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate. Palea of the proximal incomplete florets fully developed. The proximal incomplete florets male. The proximal lemmas awnless; 3–7 nerved; decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas (often hairy, resembling the upper glume); not becoming indurated.
Female-fertile florets 1 (dorsally compressed). Lemmas decidedly firmer than the glumes (cartilaginous to sub-crustaceous); smooth; becoming indurated to not becoming indurated; entire to incised; not deeply cleft (obtuse to emarginate); awnless; hairless (shiny); non-carinate; having the margins lying flat on the palea; 3–5 nerved. Palea present; relatively long; tightly clasped by the lemma; entire; textured like the lemma; 2-nerved. Lodicules present; 2; free; glabrous; not or scarcely vascularized. Stamens 3. Ovary glabrous. Styles fused, or free to their bases.
Fruit, embryo and seedling. Fruit free from both lemma and palea (but enclosed); compressed dorsiventrally. Hilum short. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells having markedly sinuous walls. Microhairs present; panicoid-type; 51–66 microns long; 5.4–6 microns wide at the septum. Microhair total length/width at septum 8.5–12.2. Microhair apical cells 24–39 microns long. Microhair apical cell/total length ratio 0.47–0.59. Stomata common; 30–36 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs. Costal zones with short-cells. Costal short-cells mixture on the one epidermis. Costal silica bodies ‘panicoid-type’; cross shaped (some), or nodular (mostly); not sharp-pointed.
Transverse section of leaf blade, physiology. C4; XyMS+. PCR sheath outlines uneven. PCR cell chloroplasts centrifugal/peripheral. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section to adaxially flat; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only to having a conventional arc of bundles (depending on delimitation of mid-rib). Bulliforms present in discrete, regular adaxial groups; in simple fans. Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 9. 2n = 36. 4 ploid.
Taxonomy. Panicoideae; Panicodae; Paniceae (Melinideae).
Distribution, ecology, phytogeography. 12 species; Africa, Madagascar, Canaries, Mediterranean. Xerophytic; species of open habitats; glycophytic. Sandy and stony soil, sometimes ruderal.
Holarctic, Paleotropical, Neotropical, and Cape. Tethyan. African and Madagascan. Macaronesian, Mediterranean, and Irano-Turanian. Saharo-Sindian, Sudano-Angolan, and Namib-Karoo. Andean. Sahelo-Sudanian, Somalo-Ethiopian, South Tropical African, and Kalaharian.
Rusts and smuts. Rusts — Physopella. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca and Ustilago.
Economic importance. Important native pasture species: T. teneriffae.
References, etc. Leaf anatomical: this project.
Illustrations. • General aspect. • Abaxial epidermis of leaf blade
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
