Leymus mollis |
Poaceae tribe Triticeae |
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American dunegrass, American lyme grass, dune wildrye, dunegrass, elyme des sables d'amerique, sea lyme-grass, seigle de mer |
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Habit | Plants not cespitose, strongly rhizomatous, occasionally slightly glaucous. | Plants annual or perennial; sometimes cespitose, sometimes rhizomatous. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Culms | 12-170 cm tall, 3-6 mm thick, usually densely pubescent below the spikes for 10-40+ mm. |
annual, not woody, usually erect, not branching above the base; internodes hollow or solid. |
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Sheaths | usually open, those of the basal leaves sometimes closed; collars without tufts of hair on the sides; auricles usually present; ligules membranous or scarious, sometimes ciliolate, those of the upper and lower cauline leaves usually similar; pseudopetioles absent; blades linear to narrowly lanceolate, venation parallel, cross venation not evident, without arm or fusoid cells, surfaces without microhairs, not papillate, cross sections non-Kranz. |
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Leaves | exceeded by the spikes; auricles to 0.7 mm; ligules 0.2-2.5 mm; blades 10-94 cm long, 3-15 mm wide, adaxial surfaces scabridulous to scabrous, 20-40-veined, veins subequal, prominently ribbed, closely spaced. |
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Inflorescences | usually spikes or spikelike racemes, with 1-5 sessile or subsessile spikelets per node, occasionally panicles, sometimes with morphologically distinct sterile and bisexual spikelets within an inflorescence; pedicels absent or to 4 mm; disarticulation usually above the glumes and beneath the florets, sometimes in the rachises, sometimes at the inflorescence bases. |
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Spikes | 5-34 cm long, 10-20 mm wide, with 3-33 nodes, usually with 2 spikelets per node; internodes 4.5-9.5 mm, surfaces and edges similar, hairs on the surfaces 0.1-0.5 mm, on the edges to 0.7 mm. |
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Spikelets | 15-34 mm, with 3-6 florets. |
usually laterally compressed, sometimes terete, with 1-16 bisexual florets, the distal (or only) floret sometimes sterile; rachillas sometimes prolonged beyond the base of the distal floret. |
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Glumes | 9-34 mm long, 1.5-4 mm wide, lanceolate, tapering from midlength or above, flat or rounded on the back, flexible, usually strigillose to pilose or villous, rarely almost glabrous, the central portion scarcely thicker than the margins, 3(5)-veined at midlength, apices acute; lemmas 11-20 mm, densely hairy, hairs 0.5-1 mm, soft, apices acute, unawned; anthers 4-9 mm, dehiscent. |
unequal to equal, shorter than to longer than the adjacent florets, subulate, lanceolate, rectangular, ovate, or obovate, 1-5-veined, absent or vestigial in some species; florets laterally compressed to terete; calluses glabrous or hairy; lemmas lanceolate to rectangular, stiffly membranous to coriaceous, sometimes keeled, 5(7)-veined, veins not converging distally, inconspicuous, apices entire, lobed, or toothed, unawned or awned, awns terminal, unbranched, lemma-awn junction not evident; paleas usually subequal to the lemmas, sometimes considerably shorter or slightly longer than the lemmas; lodicules 2, without venation, usually ciliate; anthers 3; ovaries with hairy apices; styles 2, bases free. |
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Caryopses | ovoid to fusiform, longitudinally grooved, not beaked, pericarp thin; hila linear; embryos about 1/3 as long as the caryopses. |
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x | = 7. |
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Leymus mollis |
Poaceae tribe Triticeae |
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Distribution |
AK; CA; IL; MA; ME; MI; NH; OR; PA; WA; WI; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Greenland
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Discussion | Leymus mollis is native to Asia and North America. It is treated here as having two very similar subspecies that have somewhat different ranges. The subspecies are sometimes treated as separate species, but they may be little more than environmentally induced variants. Both subspecies grow primarily on coastal beaches, close to the high tide line, and along some inland waterways, particularly in the arctic. Reports of L. ajanensis (V.N. Vassil.) Tzvelev from North America are based on specimens of L. mollis (D. Murray, University of Alaska, pers. comm. 2006). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The Triticeae are primarily north-temperate in distribution. The tribe includes 400-500 species, among which are several important cereal, forage, and range species. Its generic treatment is contentious. Linnaeus (1753) recognized five genera among the species now included in the tribe; Hordeum and Secale are the only two that still have his circumscription. Hordeum is also the only genus to include both annual and perennial species. The lack of agreement concerning the generic treatment of the tribe reflects the prevalence of natural hybridization, introgression, polyploidy, and reticulate relationships among its species. These factors preclude the circumscription of monophyletic groups, and mitigate against the delineation of morphologically coherent groups. Tzvelev (1975) argued that these same factors contribute to the tribe's success by maintaining a "generalist" genome. The major disagreement in the treatment of the annual genera concerns Triticum and Aegilops. Some (e.g., Kimber and Feldman 1987) advocate treating them as a single genus in recognition of their close genetic similarity; others argue for maintaining them as separate genera (e.g., van Slageren 1994). Love (1984) divided them among 14 genera. They are accepted here in their traditional senses, despite the strong argument for their combination, largely in deference to the wealth of literature, reports, and genetic resources that have been accumulated under these two names. Spontaneous hybridization and introgression between the two are common, and most species of Triticum are derived from hybrids between the two genera. Nevertheless, they differ in their ecology and, to some extent, in their morphology. Treatment of the perennial species is more contentious. Restriction of Agropyron to what are known in English as the crested wheatgrasses is universally accepted; most taxonomists also accept the placement of alkaline-tolerant species that are strongly rhizomatous or have short, subulate glumes in Leymus. Pseudoroegneria, Pascopyrum, and Thinopyrum are less accepted. They are widely accepted by those working in genetic resources, but less so by those involved in floristics who prefer to include them in Elymus; all were traditionally included in Agropyron. Another area of disagreement is the treatment of Elytrigia Desv., Roegneria K. Koch, and Hystrix Moench. Species sometimes placed in Elytrigia are here included in Elymus, Thinopyrum, or Pseudoroegneria; species of Roegneria in Elymus; and species of Hystrix in Elymus or Leymus. Wide acceptance of a single treatment is hampered by the existence of differing taxonomic traditions, and by the lack of a coordinated international examination of morphological variation among the tribe's species. The treatment followed here is strongly influenced by the treatments of Love (1984) and Dewey (1984), particularly with respect to the perennial genera. Both advocated using genomic constitution as the basis for generic delimitation in the tribe. The genomic constitution of individual species is determined by observing meiotic chromosome pairing in hybrids. The base chromosome number in the tribe is seven. If a hybrid between two tetraploids forms 7 quadrivalents and 14 bivalents at meiosis, its parents are considered to have one similar set of chromosomes or haplome, and one dissimilar haplome. The three haplomes can then be assigned codes. For example, one parent might be said to have the E and F haplomes, or an EF genomic constitution, and the other the E and L haplomes, or an EL genomic constitution. The prevalence of polyploids and the ease of forming hybrids in the Triticeae has enabled cytogeneticists to build up a rather complete picture of the genomic constitution of its members. This led to the discovery that there is a strong, but not perfect, correlation between morphology and genomic constitution. The haplome codes used in this volume are those endorsed by the International Triticeae Consortium (http://herbarium.usu.edu/Triticeae/genmsymb.htm). Molecular tools reveal a pattern that is, in general, consistent with the cytogenetic data, but they often reveal an underlying complexity that cannot be discerned using only classical cytogenetic techniques. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 356. | FNA vol. 24, p. 238. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Triticeae > Leymus | Poaceae > subfam. Pooideae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | Elymus mollis, Elymus arenarius var. villosus, Elymus arenarius var. mollis, Elymus arenarius subsp. mollis | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (Trin.) Pilg. | Dumort. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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