The grass genera of the world
Habit, vegetative morphology. Perennial; rhizomatous. Culms 30–60 cm high; herbaceous; to 2 cm in diameter; unbranched above. Culm nodes glabrous. Rhizomes leptomorph. Plants unarmed. Leaves not basally aggregated; non-auriculate. Leaf blades narrow; 2–8 mm wide; not pseudopetiolate; without cross venation. Ligule a fringed membrane. Contra-ligule present (the adaxial ligule continued as a fringe of hairs around the back).
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate (small); open; with capillary branchlets; espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.
Female-fertile spikelets. Spikelets 9–11 mm long; compressed laterally; disarticulating above the glumes; disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairy (with long white hairs, above the disarticulation zones); the rachilla extension with incomplete florets. Hairy callus present (slender).
Glumes two; very unequal; shorter than the adjacent lemmas; hairless; glabrous; pointed; awnless; non-carinate; very dissimilar. 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 merely underdeveloped.
Female-fertile florets 3–6. Lemmas acuminate; similar in texture to the glumes (herbaceous/membranous); not becoming indurated; entire (or sometimes with a slight notch); pointed; awned. Awns 1; median; apical; non-geniculate; hairless (scabrid); much shorter than the body of the lemma to about as long as the body of the lemma. Lemmas hairy (along the margins); non-carinate (rounded); having the margins lying flat on the palea; without a germination flap; 3 nerved. Palea present; relatively long; slightly apically notched; awnless, without apical setae; not indurated (thinly membranous); 2-nerved; 2-keeled. Lodicules present; free; fleshy; glabrous; heavily vascularized. Stamens 3. Anthers not penicillate; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; brown (apparently).
Fruit, embryo and seedling. Fruit free from both lemma and palea. Pericarp free. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type (both cells long, the apical very flimsy); (44–)48–60(–62) microns long. Microhair apical cells 29–39 microns long. Microhair apical cell/total length ratio 0.62. Stomata absent or very rare. Intercostal short-cells common; not paired (solitary); not silicified. Costal prickles present. Crown cells absent. Costal short-cells conspicuously in long rows (some veins), or neither distinctly grouped into long rows nor predominantly paired (the long-cells often short). Costal silica bodies panicoid-type; cross shaped, butterfly shaped, and dumb-bell shaped, or nodular.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with fusoids (seemingly), or without fusoids (need to see fresh material). Leaf blade adaxially flat (low abaxial ribs). Midrib conspicuous (a larger bundle, with a slight double keel); with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with all the bundles); forming figures (in the midrib). Sclerenchyma all associated with vascular bundles.
Phytochemistry. Leaves without flavonoid sulphates (H. macra).
Cytology. 2n = 50.
Classification. Watson & Dallwitz (1994): Arundinoideae; Arundineae. Soreng et al. (2015): Arundinoideae; Molinieae. 1 species (H. macra).
Distribution, phytogeography, ecology. Japan.
Mesophytic; glycophytic. On wet cliffs.
References, etc. Leaf anatomical: Metcalfe 1960, and studied by us.
Special comments. Fruit data wanting.
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. delta-intkey.com/grass’.