The grass genera of the world
~ Coelachyrum, Disaksperma
Type species: C. yeminica (Schweinf.) Chiov.
Habit, vegetative morphology. Perennial; densely caespitose. Culms 30–100 cm high; herbaceous. Culm nodes glabrous. Plants unarmed. Leaves not basally aggregated. Leaf blades linear; narrow; usually flat; without abaxial multicellular glands; without cross venation. Ligule a fringed membrane.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence of spicate main branches; non-digitate. Primary inflorescence branches 2–8 (these distant, erect). Spikelet-bearing axes spicate racemes; persistent. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches; solitary; secund; biseriate; shortly pedicellate.
Female-fertile spikelets. Spikelets 5–10 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairless; not pointed (obtuse); awnless; carinate to non-carinate (rounded to slightly keeled on the back); similar (lanceolate, membranous). Lower glume 1 nerved. Upper glume usually 1 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets male. Spikelets without proximal incomplete florets.
Female-fertile florets 7–10. Lemmas not saccate; decidedly firmer than the glumes (membranous, becoming cartilaginous below); not becoming indurated; entire; pointed, or blunt (acute or obtuse); awnless; hairy (pilose with club-shaped hairs on the lower back); 3 nerved. Palea present; conspicuous but relatively short (about half the lemma length); entire (obtuse); awnless, without apical setae; not indurated (hyaline). Lodicules present (minute); 2; free; fleshy; glabrous. Stamens 3. Ovary apically glabrous (?). Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit small (1.2–1.4 mm long); compressed dorsiventrally (concavo-convex); smooth. Hilum short. Pericarp free. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; intercostal (conspicuous). Intercostal papillae over-arching the stomata (at one end); consisting of one oblique swelling per cell. Long-cells markedly different in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (medium thick walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls to having straight or only gently undulating walls. Microhairs present; more or less spherical to elongated; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhair basal cells 21 microns long. Microhair total length/width at septum 3. Microhair apical cell/total length ratio 0.4. Stomata common. Subsidiaries non-papillate; low to high dome-shaped. Guard-cells overlapped by the interstomatals (mostly, slightly). Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Prickles abundant costally. Crown cells absent. Costal short-cells conspicuously in long rows. Costal silica bodies present in alternate cell files of the costal zones; large saddle shaped.
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 absent. PCR cell chloroplasts centripetal. Leaf blade nodular in section to adaxially flat; with the ribs very irregular in sizes. Midrib conspicuous; having a conventional arc of bundles (a large bundle, flanked on each side by two smaller ones); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the larger bundles); forming figures. Sclerenchyma all associated with vascular bundles. The lamina margins with fibres.
Classification. Watson & Dallwitz (1994): Chloridoideae; main chloridoid assemblage. Soreng et al. (2015): Chloridoideae; Cynodonteae. 1 species (C. yeminica (Schweinf.) Chiov.).
Distribution, phytogeography, ecology. Northeast to southeast and southern Africa.
Xerophytic; species of open habitats.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Uromyces eragrostidis.
References, etc. Leaf anatomical: this project.
Illustrations. • C. yemenica, abaxial epidermis of leaf blade: this project
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. delta-intkey.com/grass’.