Zonotriche Phipps
Including Mitwabochloa Phipps, Piptostachya (C. E. Hubbard) Phipps
Habit, vegetative morphology. Perennial; caespitose. Culms 60–150 cm high; herbaceous. Leaves not basally aggregated. Leaf blades linear; broad to narrow; flat; without cross venation; a fringe of hairs.
Reproductive organization. Plants bisexual, with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open to contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes disarticulating; falling entire (the villous peduncle developing a fracture zone, so that the spikelet triads fall entire). Spikelets in triplets (compact); not secund; pedicellate (the pedicels connate in the triplet).
Female-fertile spikelets. Spikelets 10–28 mm long; brown; disarticulating above the glumes and falling with the glumes; disarticulating between the florets. Rachilla terminated by a female-fertile floret. Hairy callus present (beneath the L2). Callus short; blunt.
Glumes two; very unequal to more or less equal; (the longer) long relative to the adjacent lemmas; hairy (with tubercle-based hairs); without conspicuous tufts or rows of hairs; pointed; awnless; similar (narrowly lanceolate, papery to leathery). Lower glume 3 nerved. Upper glume 3 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; male. The proximal lemmas 5 nerved; exceeded by the female-fertile lemmas (2/3 to 3/4 as long as the spikelet).
Female-fertile florets 1. Lemmas thinly leathery; not becoming indurated; incised; 2 lobed; deeply cleft; awned. Awns 1, or 3; median (the lateral lobes muticous), or median and lateral (the lateral lobes aristate); the median different in form from the laterals (when laterals present); from a sinus; geniculate; hairless; much longer than the body of the lemma; persistent. Lemmas hairy (variously so). The hairs in tufts, or not in tufts; in transverse rows, or not in transverse rows. Lemmas non-carinate; 5–9 nerved. Palea present; 2-nerved; 2-keeled. Palea keels winged, or wingless. Lodicules present; fleshy. Stamens 3.
Fruit, embryo and seedling. Fruit with hairs confined to a terminal tuft (or hairless). Hilum long-linear. Embryo large.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower); of similar wall thickness costally and intercostally (of medium wall thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls (these with conspicuous pits). Microhairs present; elongated; clearly two-celled; panicoid-type; (the only complete example seen) 57 microns long; 6 microns wide at the septum. Microhair total length/width at septum 9.5. Microhair apical cells 27 microns long. Microhair apical cell/total length ratio 0.47. Stomata common; 27–33 microns long. Subsidiaries low to high dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs and not paired (sometimes seemingly solitary); silicified. A few small intercostal prickles present. Crown cells absent. Costal zones with short-cells. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; dumb-bell shaped (elongated); not sharp-pointed.
Transverse section of leaf blade, physiology. C4. The anatomical organization somewhat unconventional. Seemingly XyMS+ (the primaries certainly double-sheathed, and the inner sheath seemingly empty, in the fairly well preserved material seen). PCR sheath outlines even. PCR sheath extensions absent. Leaf blade with only low, round-topped ribs over the primary bundles. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (large groups between the primary bundles); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with the primaries); forming ‘figures’ (I’s and T’s). Sclerenchyma all associated with vascular bundles.
Taxonomy. Panicoideae; Panicodae; Arundinelleae.
Distribution, ecology, phytogeography. 3 species; tropical Africa. Savanna woodland.
Paleotropical. African. Sudano-Angolan. Somalo-Ethiopian and South Tropical African.
References, etc. Leaf anatomical: this project.
Illustrations. • Abaxial epidermis of leaf blade
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).
