| # The grass genera of the world |

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

### Poecilostachys Hackel

Excluding Chloachne

Habit, vegetative morphology. Perennial; decumbent (trailing or scrambling). Culms herbaceous; where recorded, sparsely to amply branched above. The branching simple. Culm nodes glabrous. Culm internodes solid. Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; broad, or narrow; not pseudopetiolate; without cross venation; persistent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets all alike in sexuality.

Inflorescence. Inflorescence of spicate main branches, or paniculate (with several short, unilateral, spicate racemes); open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets unaccompanied by bractiform involucres, not associated with setiform vestigial branches, or subtended by solitary ‘bristles’. The ‘bristles’ when present, persisting on the axis. Spikelets paired; secund; pedicellate.

Female-fertile spikelets. Spikelets compressed laterally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas; free; pointed; awned, or awnless (or mucronate); carinate to non-carinate; similar. Lower glume 5 nerved. Upper glume 5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; sterile. The proximal lemmas awnless; 7–9 nerved; decidedly exceeding the female-fertile lemmas; similar in texture to the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas strongly laterally compressed; similar in texture to the glumes to decidedly firmer than the glumes (membranous to cartilaginous); not becoming indurated; entire; pointed; awnless; non-carinate; having the margins lying flat on the palea, or having the margins inrolled against the palea; without a germination flap; 5 nerved. Palea present; relatively long; 2-nerved; keel-less. Lodicules present; 2; joined; fleshy, or membranous; glabrous; heavily vascularized, or not or scarcely vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles fused. Stigmas 2.

Fruit, embryo and seedling. Fruit small, or medium sized; not noticeably compressed. Hilum long-linear. Embryo large; not waisted. Endosperm hard.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells markedly different in shape costally and intercostally (the costals much narrower). Intercostal zones exhibiting many atypical long-cells (many being almost square in P. festucaceus). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; elongated; clearly two-celled; panicoid-type; about 54 microns long; 3.3 microns wide at the septum. Microhair total length/width at septum 16.4. Microhair apical cells about 33 microns long. Microhair apical cell/total length ratio 0.61. Stomata common (but only bordering on the veins); 36–39 microns long. Subsidiaries low triangular, or dome-shaped, or dome-shaped and triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common, or absent or very rare (very rare in P. festucaceus); not paired; silicified. Costal short-cells conspicuously in long rows. Costal silica bodies ‘panicoid-type’; mostly nodular; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs to ‘nodular’ in section; with the ribs more or less constant in size (distant, low, round topped). Midrib fairly conspicuous; with one bundle only. Bulliforms not present in discrete, regular adaxial groups (most of the epidermis between the ribs ‘bulliform’, at least in P. festucaceus). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’ (in the major bundles). Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): Panicoideae; Panicodae; Paniceae. 20 species.

Distribution, phytogeography, ecology. Madagascar.

Shade species (forest).

References, etc. Leaf anatomical: poor material of P. festucaceus and P. viguieri studied by us.

Illustrations. • Poecilostachys hildebrandtii: Hook. Ic. Pl. 31 (1916).

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: 15th June 2025. delta-intkey.com’.

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