Apochiton C.E. Hubb.
Habit, vegetative morphology. Annual; caespitose (loosely), or decumbent. Culms 30–70 cm high; herbaceous; unbranched above. Culm nodes glabrous. Plants unarmed. Leaves not basally aggregated; non-auriculate; without auricular setae. Leaf blades linear; narrow; to 4 mm wide; flat; without abaxial multicellular glands; without cross venation; persistent; a fringed membrane (but the fringe of short cilia); truncate; 0.5 mm long. Contra-ligule absent.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (to 20 cm long); without capillary branchlets; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 6–8 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; rachilla sparsely hairy; the rachilla extension with incomplete florets. Hairy callus present. The callus hairs white. Callus blunt.
Glumes present; two; very unequal to more or less equal; shorter than the adjacent lemmas; hairless; pointed (tapered into short points); awned (shortly), or awnless (then mucronate); carinate; similar (greyish, membranous, glabrous). Lower glume 3 nerved. Upper glume 3 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets 1; merely underdeveloped.
Female-fertile florets 3–5. Lemmas similar in texture to the glumes (membranous); smooth; not becoming indurated; entire; awned. Awns 1; median; apical (attenuate from the lemma); non-geniculate; hairless (scabrid); much shorter than the body of the lemma to about as long as the body of the lemma (2–3 mm); entered by one vein; persistent. Lemmas hairy (with white hairs over the lower two thirds); somewhat carinate; without a germination flap; 3 nerved. Palea present; relatively long (but shorter than the lemma); deeply bifid; awned (the two lobes attenuate into terminal awns about 2 mm long); not indurated (membranous); 2-nerved; 2-keeled. Palea keels hairy (with white hairs). Lodicules present; free; fleshy; glabrous; not or scarcely vascularized. Stamens 3. Anthers 1 mm long. Ovary glabrous. Styles free to their bases. Stigmas 2; red pigmented.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small (about 2 mm long); ellipsoid; trigonous. Hilum short. Pericarp free. Embryo small (obscure).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present; costal and intercostal. Intercostal papillae not over-arching the stomata; consisting of one oblique swelling per cell (large but rather inconspicuous, at one end of many of the long-cells). Long-cells similar in shape costally and intercostally (the costals narrower); of similar wall thickness costally and intercostally (thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; more or less spherical; clearly two-celled; chloridoid-type. Microhair apical cell wall of similar thickness/rigidity to that of the basal cell. Microhairs (22.5–)24–27(–30) microns long. Microhair basal cells 10–11 microns long. Microhairs 9–12 microns wide at the septum. Microhair total length/width at septum 1.9–3.3. Microhair apical cells 9–12 microns long. Microhair apical cell/total length ratio 0.35–0.5. Stomata common; 30–33 microns long. Subsidiaries mostly low dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells absent or very rare. Intercostal silica bodies absent. Costal short-cells conspicuously in long rows (but the ‘short-cells’ tending to be rather long). Costal silica bodies confined to the central file(s) of the costal zones; ‘panicoid-type’ (mostly), or saddle shaped (a few, mostly over the midrib); mostly cross shaped and butterfly shaped.
Transverse section of leaf blade, physiology. Lamina mid-zone in transverse section open.
C4; XyMS+. PCR sheaths of the primary vascular bundles complete. PCR sheath extensions absent. Mesophyll traversed by columns of colourless mesophyll cells. Midrib conspicuous; with one bundle only, or having a conventional arc of bundles (one large solitary bundle, or one large bundle with two smaller laterals, depending on interpretation); with colourless mesophyll adaxially. Bulliforms present in discrete, regular adaxial groups; in simple fans, or associated with colourless mesophyll cells to form deeply-penetrating fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (but the girders short); nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.
Taxonomy. Chloridoideae; main chloridoid assemblage.
Distribution, ecology, phytogeography. 1 species; tropical East Africa. Mesophytic; species of open habitats. Savanna, in seasonally wet soils.
Paleotropical. African. Sudano-Angolan. Somalo-Ethiopian and South Tropical African.
References, etc. Morphological/taxonomic: Hubbard 1936b. Leaf anatomical: this project.
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).