The grass genera of the world
~ Elymus, Elytrigia
Habit, vegetative morphology. Perennial; caespitose. Culms 30–90 cm high; herbaceous; unbranched above. Young shoots intravaginal. Leaves not basally aggregated; auriculate. Leaf blades linear; apically flat; narrow; flat, or rolled (involute or convolute); without cross venation; persistent. Ligule an unfringed membrane; truncate. Contra-ligule absent.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets; outbreeding.
Inflorescence. Inflorescence a single spike (the spikelets appressed). Rachides hollowed (against the spikelet). Inflorescence espatheate; not comprising partial inflorescences and foliar organs. Spikelet-bearing axes usually persistent; fragile or not in P. stipifolia, where the spikelet may fall with the internode above. Spikelets solitary; not secund; distichous; sessile to subsessile; not imbricate (at least, the spikes lax by contrast with Elymus).
Female-fertile spikelets. Spikelets 18–22 mm long; compressed laterally; disarticulating above the glumes; not disarticulating between the florets. Rachilla prolonged beyond the uppermost female-fertile floret; hairless (glabrous); the rachilla extension with incomplete florets. Hairy callus present (inconspicuous). Callus short; blunt.
Glumes two; very unequal to more or less equal; shorter than the spikelets; shorter than the adjacent lemmas to long relative to the adjacent lemmas; lateral to the rachis; hairless (sometimes with a few spinules apically); pointed to not pointed (lanceolate or narrowly lanceolate); not subulate; awnless (but sometimes acuminate); non-carinate; similar. Lower glume 5–7 nerved. Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets. The distal incomplete florets merely underdeveloped. Spikelets without proximal incomplete florets.
Female-fertile florets 3–5. Lemmas linear-lanceolate; similar in texture to the glumes; entire; pointed; awnless, or awned. Awns when present, 1; apical; non-geniculate; recurving (widely divergent at maturity); much shorter than the body of the lemma to much longer than the body of the lemma (up to 30 mm long); entered by several veins. Lemmas hairless; glabrous, or scabrous; non-carinate; without a germination flap; 5 nerved; with the nerves confluent towards the tip. Palea present; relatively long (about equalling the lemma); awnless, without apical setae; thinner than the lemma; not indurated; 2-nerved; 2-keeled. Palea keels wingless. Lodicules present; 2; free; membranous; ciliate; not toothed. Stamens 3. Anthers 4–7 mm long. Ovary apically hairy. Styles free to their bases. Stigmas 2; white.
Fruit, embryo and seedling. Fruit adhering to lemma and/or palea; medium sized; longitudinally grooved; compressed dorsiventrally; with hairs confined to a terminal tuft. Hilum long-linear. Embryo small.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (walls of medium thickness). Mid-intercostal long-cells rectangular; having markedly sinuous walls (and pitted). Microhairs absent. Stomata common; (36–)37–39(–42) microns long. Subsidiaries predominantly parallel-sided. Guard-cells overlapped by the interstomatals (mostly, slightly). Intercostal short-cells common (abundant); in cork/silica-cell pairs and not paired (commonly solitary). Costal short-cells predominantly paired. Costal silica bodies rounded (mostly), or saddle shaped to crescentic (few, intergrading with the rounded forms); not sharp-pointed.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; without adaxial palisade. Leaf blade with distinct, prominent adaxial ribs; with the ribs very irregular in sizes (small, round topped alternating with large, flat topped). Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups (in all the furrows); in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present (with most of the major bundles); forming figures (Is with all the major bundles). Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14 and 28. 2 and 4 ploid. Haplomic genome content S.
Classification. Watson & Dallwitz (1994): Pooideae; Triticodae; Triticeae. Soreng et al. (2015): Pooideae; Triticodae; Triticeae; Hordeinae. About 16 species.
Distribution, phytogeography, ecology. Middle East, central Asia, northern China, western North America.
Xerophytic; species of open habitats. Drought tolerant.
Rusts and smuts. Rusts Puccinia.
References, etc. Morphological/taxonomic: Löve 1984. Leaf anatomical: this project.
Illustrations. • P. spicata, tip of a spikelet
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’.