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The grass genera of the world

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

Triplopogon Bor

From the Greek triplasios (triple, threefold) and pogon (beard), alluding to glumes with three hair-tufts.

Habit, vegetative morphology. Large, stilt-rooted annual. Culms 50–180 cm high (or more?); herbaceous. Culm nodes glabrous. Leaves not basally aggregated; non-auriculate. Leaf blades lanceolate (acuminate); broad; 10–35 mm wide; pseudopetiolate (attenuate to the base). Ligule an unfringed membrane; 1.5 mm long.

Reproductive organization. Plants bisexual, all with bisexual spikelets; without hermaphrodite florets (the L2 having a female-only floret). The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile; overtly heteromorphic (glumes of the pedicelled spikelets not hair-tufted); in both homogamous and heterogamous combinations (the lowermost pair both sterile).

Inflorescence. Inflorescence falsely paniculate (the numerous culm branches terminating in pedunculate ‘racemes’); spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs. Spikelet-bearing axes ‘racemes’ (6 or more noded); solitary; disarticulating; disarticulating at the joints. ‘Articles’ linear (to slightly widened upwards, flattened); not appendaged; disarticulating transversely; densely long-hairy (densely silky on margins). Spikelets paired; sessile and pedicellate; consistently in ‘long-and-short’ combinations; in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite, or sterile (the lowermost sessile spikelet being rudimentary, and the second pair often reduced). The ‘longer’ spikelets sterile (?).

Female-sterile spikelets. Pedicelled spikelets sterile(?), to 5 mm long.

Female-fertile spikelets. Spikelets 8–10 mm long; compressed laterally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present.

Glumes one per spikelet; relatively large; long relative to the adjacent lemmas; hairy; with distinct hair tufts (the G1 with two tufts, the G2 with one); awnless; very dissimilar (the G1 lanceolate, with a median groove and incurved margins and a hair tuft on either side above the middle, the G2 complanate, not grooved, with one median tuft). Lower glume not two-keeled (except towards the tip, and wingless); sulcate on the back; not pitted; relatively smooth; ‘many-nerved’. Upper glume ‘about 9-nerved’. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; paleate; male (the floret with 3 stamens). The proximal lemmas awnless; 3 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas (thin); not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (thin); not becoming indurated; incised; not deeply cleft; awned. Awns 1; median; from a sinus; geniculate; hairless (scabrid); much longer than the body of the lemma. Lemmas hairless; glabrous; non-carinate; without a germination flap; 3 nerved. Palea present; conspicuous but relatively short; entire; awnless, without apical setae; not indurated (thin); 2-nerved; keel-less. Lodicules present; 2; free; fleshy; glabrous. Stamens 0. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small (3.5 mm long); longitudinally grooved (adaxially); strongly compressed laterally (and 3-angled). Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell (a row per long-cell). Intercostal zones with typical long-cells to exhibiting many atypical long-cells (some of them short). Mid-intercostal long-cells having markedly sinuous walls (thin). Microhairs present; panicoid-type; (24–)31–44 microns long. Microhair apical cells (13–)16–29 microns long. Microhair apical cell/total length ratio 0.6. Stomata common. Subsidiaries tall dome-shaped and triangular. Intercostal short-cells absent or very rare (infrequent). Costal zones with short-cells. Costal short-cells conspicuously in long rows, or neither distinctly grouped into long rows nor predominantly paired (confused by long ‘short-cells’). Costal silica bodies ‘panicoid-type’; cross shaped to dumb-bell shaped, or nodular (and intermediates); not sharp-pointed.

Transverse section of leaf blade, physiology. C4 (vb’s ‘crowded’); XyMS–. Mesophyll with radiate chlorenchyma. Leaf blade adaxially flat. Midrib conspicuous (keel rounded); having a conventional arc of bundles (3 large median bundles and several smaller laterals); with colourless mesophyll adaxially. Bulliforms not present in discrete, regular adaxial groups (in irregular groups, cf. Ammophila). Many of the smallest vascular bundles unaccompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma as a hypodermal adaxial plate in the keel.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Andropogoninae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Ischaeminae. 1 species (T. ramosissimus).

Distribution, phytogeography, ecology. Bombay.

Forest margins.

Rusts and smuts. Smuts from Ustilaginaceae. Ustilaginaceae — Sphacelotheca.

References, etc. Morphological/taxonomic: Bor 1954. Leaf anatomical: Metcalfe 1960.


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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’.

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