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The grass genera of the world

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

Lecomtella A. Camus

Habit, vegetative morphology. Bamboo-like perennial. Culms about 50–200 cm high; herbaceous; branched above. Culm leaves present. Culm internodes hollow. Plants unarmed. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades lanceolate (-acuminate); broad; 10–20 mm wide (12–22 cm long); not pseudopetiolate; without cross venation. Ligule a fringe of hairs. Contra-ligule present (as a fringe of hairs).

Reproductive organization. Plants bisexual, all with bisexual spikelets; without hermaphrodite florets (the upper floret of the hermaphrodite spikelet female-only). The spikelets of sexually distinct forms on the same plant; hermaphrodite and male-only. The male and female-fertile spikelets segregated, in different parts of the same inflorescence branch (the short branches with the spikelets male-only below, hermaphrodite above). The spikelets homomorphic.

Inflorescence. Inflorescence paniculate; contracted; more or less irregular; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes with very slender rachides; persistent. Spikelets not secund; pedicellate. Pedicel apices cupuliform. Spikelets imbricate.

Female-sterile spikelets. Male spikelets similar to the hermaphrodite, but both florets male with membranous lemmas. Rachilla of male spikelets terminated by a male floret. The male spikelets with glumes; without proximal incomplete florets; 2 floreted (both male). The lemmas awnless. Male florets 2; 3 staminate.

Female-fertile spikelets. Spikelets 10 mm long (or more); weakly compressed laterally; falling with the glumes; disarticulating between the florets; with distinctly elongated rachilla internodes between the florets (the upper floret borne on a short stipe with two apical wings). The upper floret conspicuously stipitate. The stipe beneath the upper floret not filiform; straight and swollen; homogeneous. Rachilla terminated by a female-fertile floret; hairless. Hairy callus absent. Callus absent.

Glumes two; very unequal to more or less equal; shorter than the spikelets; (the longer) shorter than the adjacent lemmas; hairless; glabrous; pointed (acuminate); awnless; carinate; similar (herbaceous, ovate-lanceolate). Lower glume about 0.7 times the length of the upper glume; 3 nerved. Upper glume 7 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. Palea of the proximal incomplete florets fully developed (hyaline, two keeled). The proximal incomplete florets male (with 3 stamens). The proximal lemmas lanceolate; awnless; 7 nerved, or 9 nerved; decidedly exceeding the female-fertile lemmas (equalling the spikelet); less firm than the female-fertile lemmas (herbaceous); not becoming indurated.

Female-fertile florets 1 (female-only). Lemmas ovate; decidedly firmer than the glumes (crustaceous, tuberculate at the tip, with 3 thickened cushions apically on the nerves); becoming indurated; entire; blunt; awnless; hairy; non-carinate; having the margins lying flat on the palea; with a clear germination flap; 5 nerved; with the nerves non-confluent. Palea present; relatively long; tightly clasped by the lemma; entire (tuberculate at the tip, with thickened cushions apically on the nerves); awnless, without apical setae; textured like the lemma; thickened apically; 2-nerved; keel-less (with incurved margins). Lodicules present; 2; free; fleshy (quadrangular); glabrous; not or scarcely vascularized. Ovary apically glabrous. Styles free to their bases. Stigmas 2 (very long, slender).

Fruit, embryo and seedling. Pericarp thin.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally (of medium thickness). Intercostal zones exhibiting many atypical long-cells (these and the interstomatals frequently very short). Mid-intercostal long-cells rectangular; having markedly sinuous walls (conspicuously pitted). Microhairs seemingly absent (but these would be very hard to detect amid the nemerous prickles). Stomata common (unusually abundant). Subsidiaries non-papillate; high dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not paired (solitary, small); not silicified. With long, almost continuous chains of large, bulbous prickles costally, and with vey numerous smaller to tiny prickles intercostally; no macrohairs seen. Costal zones with short-cells. Costal short-cells predominantly paired (in places), or neither distinctly grouped into long rows nor predominantly paired (the pairs and short rows separated by prickles). Costal silica bodies present and well developed (but relatively infrequent); ‘panicoid-type’; very shortly dumb-bell shaped, or cross shaped.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade; without ‘circular cells’. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib conspicuous to not readily distinguishable (perhaps represented by a slightly enlarged primary bundle); with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (these large, in each furrow). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (all the bundles with I’s). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae (Boivinelleae). Soreng et al. (2015): Panicoideae; Panicodae; Paspaleae; Paspalinae. 1 species (L. madagascariensis).

Distribution, phytogeography, ecology. Madagascar.

Mesophytic. Forest margins.

References, etc. Morphological/taxonomic: Camus 1925b. Leaf anatomical: studied by us.

Illustrations. • Spikelets of L. madagascariensis

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.’.