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The grass genera of the world

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

Melanocenchris Nees

From the Greek melanos (black) and either cenchrus (millet) or cenchris (a snake with milletlike protuberances on its skin); thus meaning ‘black millet’ (re purple awns), or (more likely) alluding to the warty snakelike appearance of the racemes.

Including Gracilea Hook. f., Ptiloneilema Steud., Roylea Steud.

Habit, vegetative morphology. Annual, or perennial; caespitose. Culms 5–20 cm high; herbaceous. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 5–6 mm wide; setaceous, or not setaceous; exhibiting multicellular glands abaxially (base of macrohairs). The abaxial leaf blade glands intercostal. Leaf blades cross veined; persistent. Ligule 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. The male and female-fertile spikelets segregated, in different parts of the same inflorescence branch, or mixed in the inflorescence (each head commonly with 1–2 hermaphrodite spikelets and 2–3 progressively smaller male or sterile members).

Inflorescence. Inflorescence a false spike, with spikelets on contracted axes (the spikelets in turbinate heads). Inflorescence axes not ending in spikelets (the reduced raceme terminated by a forked bristle). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes very much reduced (to heads of spikelets); disarticulating; falling entire (the heads falling - the main axis persistent). Spikelets secund (the heads secund on the spikes); pedicellate.

Female-sterile spikelets. Sterile and (when present) male spikelets similar to the hermaphrodites, but more or less reduced.

Female-fertile spikelets. Spikelets 4 mm long; compressed laterally, or compressed dorsiventrally (?); falling with the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets (the second floret male or sterile, with an extension above). Hairy callus present.

Glumes two; very unequal to more or less equal; shorter than the adjacent lemmas to long relative to the adjacent lemmas; hairy (G1 hairy on the back and at the base of the awn, G2 hairy on the nerves and at the base of the awn); awned (both G1 and G2 with their mid-nerve produced into a purplish, scabrid awn); very dissimilar (the lower linear, the upper with broad hyaline wings). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1.

Female-fertile florets 1. Lemmas lobed/awned, except for the L1 of M. monoica; not becoming indurated; incised; 3 lobed (the lobes acuminate-awned); deeply cleft (above); awned. Awns 3; median and lateral; the median similar in form to the laterals; from a sinus; non-geniculate; much shorter than the body of the lemma. The lateral awns somewhat shorter than the median. Lemmas hairy (covered with short clavate hairs); carinate; 3 nerved. Palea present; relatively long; apically notched to deeply bifid; with apical setae to awned; 2-nerved; 2-keeled (abaxially covered with clavate hairs). Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small; ellipsoid; compressed dorsiventrally. Hilum short. Pericarp fused. Embryo large; not waisted.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae over-arching the stomata; consisting of one symmetrical projection per cell (finger-like). Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs 61.5–66 microns long. Microhair basal cells 54 microns long. Microhairs 15–17.5 microns wide at the septum. Microhair total length/width at septum 3.2–4.2. Microhair apical cells 10.5–12.9 microns long. Microhair apical cell/total length ratio 0.17–0.21. Stomata common; (19.5–)21 microns long. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare (none seen). Intercostal silica bodies absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; saddle shaped, tall-and-narrow, and crescentic; not sharp-pointed.

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

C4; XyMS+. PCR sheaths of the primary vascular bundles interrupted; interrupted abaxially only to interrupted both abaxially and adaxially. PCR sheath extensions absent. Mesophyll with radiate chlorenchyma. Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins without fibres.

Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae; Tripogoninae. 3 species.

Distribution, phytogeography, ecology. Northeastern tropical Africa, India, Ceylon.

Species of open habitats. Dry plains and hillsides.

References, etc. Leaf anatomical: studied by us - M. abyssinica (R. Br.) Hochst.

Illustrations. • M. jacquemontii: 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: 11th December 2017.’.