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The grass genera of the world

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

Lasiurus Boiss.

From the Greek lasios (hairy) and oura (tail), referring to an erect, hairy inflorescence.

Type species: L. scindicus Henrard.

Including Loxodera Launert p.p.

Habit, vegetative morphology. Perennial; caespitose. Culms woody and persistent to herbaceous (woody and persistent at the base). Young shoots intravaginal. Leaves non-auriculate. Leaf blades not pseudopetiolate; without cross venation. Ligule present; a fringed membrane to a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only, or hermaphrodite and sterile; overtly heteromorphic to homomorphic (the G1 of the pedicelled members not tailed); all in heterogamous combinations.

Inflorescence. Inflorescence of spicate main branches (of terminal, silky-hairy spiciform racemes); open; digitate, or subdigitate, or non-digitate; spatheate; a complex of ‘partial inflorescences’ and intervening foliar organs (with spathaceous sheaths). Spikelet-bearing axes ‘racemes’; solitary; with substantial rachides; disarticulating; disarticulating at the joints. ‘Articles’ non-linear (stoutly clavate); with a basal callus-knob; appendaged (the appendages suborbicular); disarticulating transversely; densely long-hairy (bearded at the nodes). Spikelets paired and in triplets (mostly triplets); not secund (the sessile spikelets alternating); sessile and pedicellate (the pedicels resembling the internodes); consistently in ‘long-and-short’ combinations (two sessile and one pedicelled spikelet per triplet); in pedicellate/sessile combinations. Pedicels of the ‘pedicellate’ spikelets free of the rachis. The ‘shorter’ spikelets hermaphrodite. The ‘longer’ spikelets male-only, or sterile.

Female-sterile spikelets. The pedicellate spikelets well developed, with tailless G1.

Female-fertile spikelets. Spikelets compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus present.

Glumes two; very unequal; (the longer) long relative to the adjacent lemmas; hairy (G1 densely ciliate); awnless; very dissimilar (the lower flat-backed, bicarinate above, subleathery and hairy with a short bidentate or flattened apical extension, the upper naviculate and membranous). Lower glume flattened on the back; not pitted; relatively smooth. 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 nerved; similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas less firm than the glumes (hyaline); not becoming indurated; entire; pointed; awnless; hairless; carinate; 3 nerved. Palea present; relatively long; entire; awnless, without apical setae; not indurated (hyaline); 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; compressed dorsiventrally. Hilum short. Embryo large.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally to markedly different in shape costally and intercostally (the costals bulbous between the silica cells, elsewhere more regularly rectangular); of similar wall thickness costally and intercostally to differing markedly in wall thickness costally and intercostally (thick walled, the costals tending to be thicker). Intercostal zones with typical long-cells, or exhibiting many atypical long-cells (in places). Mid-intercostal long-cells rectangular; having markedly sinuous walls (with conspicuous pitting, including in the outer wall). Microhairs present, or absent (seemingly, in the material seen); when recorded, panicoid-type. Stomata common. Subsidiaries non-papillate; triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (mostly, seemingly solitary), or in cork/silica-cell pairs (sometimes, adjoining the costal zones); silicified (in places), or not silicified (mainly). The costal zones with small to large prickles, grading into macrohairs. Costal short-cells predominantly paired (mostly), or neither distinctly grouped into long rows nor predominantly paired (in places, solitary or in short rows). Costal silica bodies present and well developed; more or less ‘panicoid-type’, or rounded; mostly cross shaped (but with only slight furrowing).

Transverse section of leaf blade, physiology. C4. The anatomical organization conventional. XyMS–. PCR sheath extensions absent. Mesophyll traversed by columns of colourless mesophyll cells (perhaps, in places), or not traversed by colourless columns. Leaf blade with distinct, prominent adaxial ribs; with the ribs more or less constant in size (low, wide). Midrib very conspicuous; having a conventional arc of bundles (three primaries, separated by minor bundles); with colourless mesophyll adaxially (this extending outwards beneath the bulliform ‘hinges’). The lamina symmetrical on either side of the midrib. Bulliforms present in discrete, regular adaxial groups (with a large group in each furrow, overlying small vascular bundles); associated with internal colourless tissue, the latter thinner walled and extending inwards asymmetrically; associating with colourless mesophyll cells to form arches over small vascular bundles. Many of the smallest vascular bundles unaccompanied by sclerenchyma (most but not all of the smallest bundles being associated with a small sclerenchyma group). Combined sclerenchyma girders present to absent (perhaps present with a few primaries, but in most cases there is only an adaxial strand, with colourless tissue intervening). Sclerenchyma all associated with vascular bundles.

Phytochemistry. Leaves without flavonoid sulphates (1 species).

Cytology. Chromosome base number, x = 7, or 9. 2n = 18 and 56. 2 and 6 ploid.

Classification. Watson & Dallwitz (1994): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. Soreng et al. (2015): Panicoideae; Andropogonodae; Andropogoneae; Rottboelliinae. 3 species (with species now referred to Loxodera included).

Distribution, phytogeography, ecology. Tropical East Africa, India.

Xerophytic; species of open habitats. Subdesert.

Economic aspects. Important native pasture species: L. scindicus, in arid conditions.

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

References, etc. Leaf anatomical: Metcalfe 1960; this project.

Illustrations. • cf. L. scindicus (as L. hirsutus): Fl. Iraq, 1968

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: 13th November 2017.’.