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The grass genera of the world

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

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; neither leathery nor flimsy; broad to narrow; flat; without cross venation. Ligule a fringe of hairs.

Reproductive organization. Plants bisexual, all 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); not in distinct ‘long-and-short’ combinations.

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.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Arundinelleae. Soreng et al. (2015): Panicoideae; Tristachyideae. 3 species.

Distribution, phytogeography, ecology. Tropical Africa.

Savanna woodland.

References, etc. Leaf anatomical: studied by us - Z. inamoena (K. Schum.) Phipps.

Illustrations. • Z. decora: Clayton, Flora Zambesiaca 10 (1989). • Z. inamoena, 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: 11th December 2017.’.