Monelytrum Hackel
Habit, vegetative morphology. Annual, or perennial; stoloniferous (each ‘stolon’ being a single, bare internode), or caespitose, or decumbent. Culms 8–80 cm high; herbaceous; branched above, or unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 2–7 mm wide (their margins thickened, with tubercle-based hairs); somewhat cordate; flat, or rolled (convolute); without abaxial multicellular glands; without cross venation; persistent; a fringed membrane; 1 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; hermaphrodite and sterile (there being 1–3 sterile spikelets at the tips of the reduced inflorescence branches); overtly heteromorphic (the sterile spikelets more or less awn-like); all in heterogamous combinations.
Inflorescence. Inflorescence bristly, a false spike, with spikelets on contracted axes. Inflorescence axes not ending in spikelets (but rather, ending in bristles representing the uppermost 1–3 spikelets). Inflorescence espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes very much reduced (to shortly pedunculate spikelet clusters); disarticulating; falling entire (i.e., the clusters shed). Spikelets solitary; not secund; sessile to pedicellate; imbricate.
Female-sterile spikelets. The sterile spikelets awnlike, at the tips of the reduced branches.
Female-fertile spikelets. Spikelets 3–4 mm long; adaxial; compressed dorsiventrally; planoconvex; falling with the glumes (in the glomerules); with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus present (at the base of the cluster). Callus long (formed from the rachis base); blunt.
Glumes one per spikelet (G1 sometimes absent), or two; (the upper) relatively large; very unequal; (the upper) long relative to the adjacent lemmas; hairy; (the upper) awned (with a slightly recurved awn at least as long as itself); non-carinate; very dissimilar (G1 reduced to a minute scale, G2 flat, elliptic-lanceolate, herbaceous). Lower glume much shorter than half length of lowest lemma (minute); 0 nerved. Upper glume 5–7 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas less firm than the glumes (membranous); not becoming indurated; entire to incised; pointed; when incised, minutely 3 lobed; not deeply cleft; mucronate to awned (from the mid-nerve). Awns when present, 1; median; apical; non-geniculate; hairless (scaberulous); much shorter than the body of the lemma; entered by one vein. Lemmas sparsely hairy; non-carinate; without a germination flap; 3 nerved. Palea present (broadly lanceolate); relatively long; entire (truncate); awnless, without apical setae (with scattered hairs); slightly thinner than the lemma; not indurated; 2-nerved; 2-keeled. Lodicules present; 2; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 2 mm long; not penicillate; without an apically prolonged connective. Ovary glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (2 mm long); ellipsoid; compressed dorsiventrally (dorsally). Hilum short (elliptical). Pericarp fused. Embryo large (about 1/3 the length of the fruit); not waisted.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal. Intercostal papillae consisting of one oblique swelling per cell (at one end of each interstomatal cell). Long-cells differing markedly in wall thickness costally and intercostally (intercostal walls thicker). Mid-intercostal long-cells rectangular (very); 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 (39–)42–45(–51) microns long. Microhair basal cells 33 microns long. Microhairs 12–14.4 microns wide at the septum. Microhair total length/width at septum 2.9–4.3. Microhair apical cells (9–)10.5–12(–15) microns long. Microhair apical cell/total length ratio 0.23–0.33. Stomata common; 27–33 microns long. Subsidiaries dome-shaped and triangular. Guard-cells stomata sunken below the raised (concave) ends of the interstomatals, but not overlapped. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows (but the ‘short-cells’ often rather long, giving an impression of some pairs and short rows). Costal silica bodies present in alternate cell files of the costal zones; almost exclusively saddle shaped; not sharp-pointed.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheath outlines even. PCR sheaths of the primary vascular bundles complete to interrupted; interrupted adaxially only. PCR sheath extensions absent. PCR cell chloroplasts centripetal. Leaf blade adaxially flat (with low abaxial ribs). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans (the large median cells deeply penetrating), or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries - some minor bundles with strands only); forming ‘figures’. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 2 species; southwest Africa to southern Angola. Xerophytic; species of open habitats; glycophytic. In seasonally moist locations?.
Paleotropical. African. Namib-Karoo.
References, etc. Leaf anatomical: Metcalfe 1960; this project; photos of M. luderitzianum provided by R.P. Ellis.
Illustrations. • General aspect
Cite this publication as: Watson, L., and Dallwitz, M. J. (1992 onwards). ‘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.’ http://biodiversity.uno.edu/delta/. Version: 18th August 1999. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993 onwards, 1998), and Watson and Dallwitz (1994), and Watson, Dallwitz, and Johnston (1986) should also be cited (see References).
