The grass genera of the world
Type species: Type: H. odorata (L.) Wahlenb. (type cons.).
Including Ataxia R. Br., Dimeria Raf., Disarrenum Labill., Savastana Schrank, Torresia Ruiz & Pavon
Habit, vegetative morphology. Perennial; rhizomatous, or caespitose. Culms 7–120 cm high; herbaceous; branched above to unbranched above. The branching simple. Culm nodes glabrous. Culm internodes hollow. Young shoots extravaginal. The shoots aromatic (coumarin-scented). Leaves not basally aggregated; non-auriculate. Leaf blades linear to lanceolate; apically flat; narrow; flat, or folded, or rolled; without cross venation; persistent; rolled in bud. Ligule an unfringed membrane; not truncate; 2–5.5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. Apomictic, or reproducing sexually.
Inflorescence. Inflorescence paniculate; open; with capillary branchlets, or without capillary branchlets. Primary inflorescence branches inserted all around the main axis. Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes persistent. Spikelets not secund.
Female-fertile spikelets. Spikelets 3.5–7 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets. Rachilla terminated by a female-fertile floret. Hairy callus absent.
Glumes two; very unequal to more or less equal; about equalling the spikelets; shorter than the adjacent lemmas, or long relative to the adjacent lemmas; pointed; awnless; carinate; similar (membranous, ovate). Lower glume 1–5 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2; paleate; male (with 3 stamens, or rarely neuter). The proximal lemmas awned, or awnless; 5 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; less firm than the female-fertile lemmas (membranous); not becoming indurated.
Female-fertile florets 1. Lemmas becoming indurated (usually), or not becoming indurated (in only 1 species); entire; blunt; awnless, or mucronate, or awned. Awns when present, 1; dorsal; from near the top; non-geniculate; much shorter than the body of the lemma; entered by one vein. Lemmas hairy, or hairless; non-carinate; 3–5(–7) nerved. Palea present; relatively long; 1-nerved; keel-less (2-keeled in male florets). Lodicules present; 2; free; membranous; glabrous; toothed, or not toothed. Stamens 2 (3 in male florets). Anthers 1–3.5 mm long; not penicillate. Ovary apically glabrous. Styles fused, or free to their bases. Stigmas 2; white, or brown.
Fruit, embryo and seedling. Fruit free from both lemma and palea; small; compressed laterally. Hilum short. Embryo small; not waisted. Endosperm hard; with lipid; containing compound starch grains. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
First seedling leaf with a well-developed lamina. The lamina narrow; 3–5 veined.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; differing markedly in wall thickness costally and intercostally (the costals thicker). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs absent. Stomata common, or absent or very rare. Subsidiaries low dome-shaped, or parallel-sided. Intercostal short-cells common, or absent or very rare. Costal short-cells conspicuously in long rows (rarely), or neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous, or horizontally-elongated smooth.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade nodular in section; with the ribs more or less constant in size. Midrib conspicuous, or not readily distinguishable; with one bundle only, or having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups (in the furrows); in simple fans (and sometimes in ill-defined groups of small cells, cf. Ammophila). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures, or nowhere forming figures. Sclerenchyma all associated with vascular bundles.
Phytochemistry. Leaves without flavonoid sulphates (1 species).
Cytology. Chromosome base number, x = 7. 2n = 14, 28, 42, 56, 64, 66, 68, 71, and 72, or 74–78. 2, 4, 6, 8, 9, 10, and 11 ploid (and aneuploids). Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Aveneae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Anthoxanthinae. 30 species.
Distribution, phytogeography, ecology. Temperate & cold regions.
Helophytic to mesophytic; shade species and species of open habitats. Woods, marshes, grasslands, tundra.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia graminis, Puccinia coronata, Puccinia praegracilis, and Puccinia recondita. Smuts from Tilletiaceae and from Ustilaginaceae. Tilletiaceae Urocystis. Ustilaginaceae Ustilago.
References, etc. Morphological/taxonomic: Schouten and Veldkamp 1985. Leaf anatomical: Metcalfe 1960; this project.
Illustrations. • Inflorescence detail (H. redolens). • H. redolens, opened spikelet showing details: this project. Hierochloe redolens. Two proximal incomplete florets with short-awned lemmas. • H. rariflora: Hooker, Fl. Tasmaniae (1860). • Spikelets of H. rariflora. • Dissected spikelet of H. rariflora. • H. rariflora, abaxial epidermis of leaf blade: this project. • H. rariflora, abaxial epidermis of leaf blade: this project. • H. brunonis: Hooker, Fl. Antarctica (1844). • H. odorata (as H. borealis): Eng. Bot. (1872)
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: 13th November 2017. delta-intkey.com/grass’.