| # The grass genera of the world |

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

### Silentvalleya Nair, Sreekumar, Vajravelu & Bhargavan

Name alluding to the Silent Valley Reserve Forest, Aruvampara.

Habit, vegetative morphology. Perennial; caespitose. Culms 40–100 cm high; herbaceous; unbranched above. Culm nodes glabrous. Leaves non-auriculate. Leaf blades linear (with filiform tips); narrow; 0.4–0.6 mm wide; without abaxial multicellular glands; without cross venation. Ligule an unfringed membrane (according to the original description); truncate.

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

Inflorescence. Inflorescence of spicate main branches; non-digitate (the slender ‘racemes’ scattered along a main axis). Primary inflorescence branches 6–10. Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. The racemes spikelet bearing to the base. Spikelet-bearing axes persistent. Spikelets solitary (at each node); secund (obscurely so?); biseriate; subsessile; imbricate.

Female-fertile spikelets. Spikelets about 8 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (except for the callus at the base of each floret); the rachilla extension with incomplete florets. Hairy callus present. Callus short.

Glumes two; very unequal (the G1 considerably the shorter); shorter than the spikelets; (the upper) long relative to the adjacent lemmas; hairless; glabrous; without conspicuous tufts or rows of hairs; pointed (G1 acute, G2 acuminate); awnless. Lower glume 0.5 times the length of the upper glume; shorter than the lowest lemma; 0 nerved. Upper glume 3 nerved (the laterals faint). Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped.

Female-fertile florets 6–10 (sometimes purplish). Lemmas lanceolate, acuminate; not becoming indurated; entire; pointed; awned. Awns 1; median; apical (from the acuminate lemma tip); non-geniculate; hairless (scabrid); about as long as the body of the lemma to much longer than the body of the lemma. Lemmas hairless; glabrous; without a germination flap; 3 nerved (the laterals faint). Palea present; relatively long; entire; awnless, without apical setae; 2-nerved; 2-keeled. Palea keels winged; hairy (ciliate). Lodicules present; 2; free; fleshy (seemingly); glabrous. Stamens 3. Anthers 1.25 mm long (the filaments relatively short); not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit small (about 2 mm long, stipitate); not noticeably compressed. Hilum short (?). Pericarp fused (seemingly). Embryo large (?).

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells rectangular. Microhairs present (but very scarce); elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 18 microns long. Microhair total length/width at septum 2.5. Microhair apical cell/total length ratio 0.4. Stomata fairly common. Intercostal short-cells in cork/silica-cell pairs; silicified. Intercostal silica bodies present and perfectly developed; tall-and-narrow. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; rounded.

Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.

C4; XyMS+. PCR sheath outlines uneven. PCR sheaths of the primary vascular bundles interrupted; interrupted both abaxially and adaxially. PCR sheath extensions present. Maximum number of extension cells 2. Mesophyll traversed by columns of colourless mesophyll cells. Leaf blade with distinct, prominent adaxial ribs. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage (cf. Diplachne). Soreng et al. (2015): Chloridoideae. 1 species (S. nairii).

Distribution, phytogeography, ecology. India.

References, etc. Morphological/taxonomic: Nair, Sreekumar, Vajravelu and Bhargavan 1982b. Leaf anatomical: Van den Borre 1994.

Illustrations. • Silentvalleya nairii: Nair et al., J. Bombay Nat. Hist. Soc. 79 (1982).

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: 15th June 2025. delta-intkey.com’.

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