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The grass genera of the world

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

Phaenosperma Munro ex Benth.

Habit, vegetative morphology. Perennial; robust, rhizomatous. Culms 100–300 cm high; herbaceous; to 0.03 cm in diameter. Culm nodes glabrous. Culm internodes solid, or hollow. Leaves not basally aggregated; non-auriculate. Leaf blades broadly linear; broad; 10–30 mm wide; flat; pseudopetiolate (at least the basal ones, becoming inverted by twisting of the ‘petiole’); pinnately veined (with nerves slanting obliquely from the midrib); cross veined; disarticulating from the sheaths (?). Ligule an unfringed membrane; not truncate (acute to rounded); 6–10 mm long. Contra-ligule absent.

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

Inflorescence. Inflorescence paniculate; open; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund; pedicellate.

Female-fertile spikelets. Spikelets 3–3.5 mm long; compressed dorsiventrally; falling with the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes two; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; basally joined; hairless; glabrous; awnless; non-carinate; very dissimilar (membranous, G1 deltoid-lanceolate, G2 oblong). Lower glume 1 nerved. Upper glume 3 nerved. Spikelets with female-fertile florets only.

Female-fertile florets 1. Lemmas similar in texture to the glumes to decidedly firmer than the glumes (membranous); not becoming indurated; entire (but splitting); blunt; awnless; hairless; glabrous; non-carinate (rounded on the back); without a germination flap; 3–7 nerved; with the nerves confluent towards the tip. Palea present; relatively long (slightly exceeding the lemma); entire; awnless, without apical setae; not indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 3 (fairly large); free; membranous; glabrous; not toothed. Stamens 3. Anthers not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.

Fruit, embryo and seedling. Fruit free from both lemma and palea (and protruding conspicuously when mature); small (2.5–3 mm long); subglobose; slightly longitudinally grooved (along the hilum); sculptured (rugose). Hilum long-linear. Pericarp free (the seed swollen and dark brown). Embryo small. Endosperm hard (ruminate); containing only simple starch grains. Embryo with an epiblast; with a scutellar tail; with a negligible mesocotyl internode; with one scutellum bundle. Embryonic leaf margins overlapping.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Mid-intercostal long-cells having straight or only gently undulating walls. Microhairs absent. Stomata common; 19.5–21–22.5 microns long. Subsidiaries very low to high dome-shaped. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies rounded (elliptical), or crescentic. Costal short-cells predominantly paired (a few short rows). Costal silica bodies rounded and crescentic; not sharp-pointed.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without arm cells; without fusoids. Leaf blade adaxially flat. Midrib conspicuous; having a conventional arc of bundles (3 bundles); with colourless mesophyll adaxially (the material seen giving the appearance of a proliferation of PBS tissue between the large median bundle and its adaxial strand of sclerenchyma). Bulliforms present in discrete, regular adaxial groups (in addition to the large ‘midrib hinges’); in simple fans (the fans wide, in the shallow furrows). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; nowhere forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Culm anatomy. Culm internode bundles in three or more rings.

Special diagnostic feature. Seed dark brown, with ruminate endosperm.

Cytology. Chromosome base number, x = 12. 2n = 24. 2 ploid.

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Phaenospermateae. Soreng et al. (2015): Pooideae; Phaenospermateae. 1 species (P. globosa).

Distribution, phytogeography, ecology. Japan, China, Korea.

Shade species; glycophytic. In warm temperate forest.

References, etc. Morphological/taxonomic: Conert 1959; Macfarlane and Watson 1980. Leaf anatomical: Metcalfe 1960and studied by us.

Illustrations. • P. globosa: Hook. Ic. Pl. 20 (1981). • P. globosa: C.C. Hsu (1975), Flora of Taiwan. • P. globosa, 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.’.