Agrostis mertensii |
Poaceae subfam. pooideae |
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agrostide de Mertens, Merten's bentgrass, northern bent, northern bentgrass |
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Habit | Plants perennial; cespitose, not rhizomatous or stoloniferous. | Plants annual or perennial; sometimes matlike, sometimes cespitose, sometimes stoloniferous, sometimes rhizomatous. | ||||||||||||||||||||||||||||||||||||
Culms | (5)10-40 cm, erect, with 2-4 nodes. |
usually hollow, sometimes solid. |
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Leaves | mostly basal or basal and cauline, basal leaves persistent; sheaths smooth or scabrous; ligules 0.7-3.3 mm, scabridulous or smooth, usually rounded, sometimes acute or truncate, erose, sometimes lacerate; blades 2.5-13 cm long, 0.5-3 mm wide, usually flat, occasionally involute or folded. |
distichous; sheaths usually open to the base, varying to closed for nearly their full length; auricles present or absent; abaxial ligules absent; adaxial ligules scarious or membranous, sometimes puberulent or scabridulous, usually not ciliate, cilia sometimes shorter than the base; pseudopetioles rarely present; blades usually linear, sometimes broadly so, venation parallel; cross sections non-Kranz, mesophyll nonradiate, adaxial palisade layer absent, fusoid and arm cells usually absent; midribs usually simple; adaxial bulliform cells present; stomates with parallel-sided subsidiary cells; epidermes usually lacking bicellular microhairs, sometimes with unicellular microhairs, papillae usually absent, when present, rarely more than 1 per cell. |
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Panicles | (2)3-10 cm long, (0.5)1.5-5 cm wide, widely ovate to lanceolate, usually open, exserted from the upper sheaths at maturity, lowest node with (1)2-5 branches; branches erect, not capillary, readily visible, smooth or sparsely scabridulous, branched above midlength, spikelets in the distal 1/2 or beyond, lower branches (1.5)2-4 cm; pedicels 0.4-6.4 mm. |
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Inflorescences | usually terminal, panicles, spikes, or racemes, usually ebracteate; disarticulation usually below the florets, sometimes below the glumes, at the rachis nodes, or at the inflorescence bases. |
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Spikelets | lanceolate to narrowly ovate, dark brown or purplish. |
usually bisexual, infrequently unisexual or mixed, usually laterally compressed or not compressed, occasionally dorsally compressed, with 1-30 sexual florets, distal floret(s) often reduced, infrequently spikelets with 1-2 reduced or staminate basal florets and a single terminal sexual floret. |
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Glumes | subequal, 2-4 mm, elliptical to lanceolate, midveins scabrous to scabridulous, at least distally, 1-veined, acute; callus hairs to 0.4 mm, sparse; lemmas 1.6-2.6 mm, smooth or scabridulous, translucent to opaque, 5-veined, veins prominent to obscure, apices acute, entire or erose, awned from just below midlength, awns (2)3-4.4 mm, geniculate, exserted, persistent; paleas absent, or to 0.1 mm and thin; anthers 3, 0.5-0.8 mm, usually shed at anthesis. |
usually 2, upper or lower glumes sometimes absent, rarely both glumes absent; lemmas without uncinate hairs, awned or not, awns single, basal to apical; paleas usually well-developed, sometimes reduced or absent; lodicules 2(3), usually lanceolate and broadly membranous distally, rarely truncate and fleshy, usually not veined or obscurely veined, sometimes distinctly veined, sometimes ciliate; anthers (1, 2)3; ovaries glabrous or sometimes hairy distally, sometimes with an apical appendage; haustorial synergids absent; styles (1)2 (-4), bases close together, sometimes fused. |
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Caryopses | 1.4-2 mm; endosperm solid. |
hila linear, elliptic, ovate, or punctate; endosperm usually hard, sometimes soft or liquid, with or without lipids, starch grains compound or simple; embryos less than 1/2 the length of the caryopses; epiblasts usually present; scutellar cleft usually absent; mesocotyl internode usually absent; embryonic leaf margins overlapping, x = 7, 10. |
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2n | = 56 [reports of 2n = 42 are for Agrostis scabra]. |
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Agrostis mertensii |
Poaceae subfam. pooideae |
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Distribution |
AK; CO; ME; MT; NC; NH; NY; SC; TN; UT; VA; VT; WA; WV; WY; AB; BC; MB; NB; NL; NT; NU; ON; QC; SK; YT; Greenland |
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Discussion | Agrostis mertensii grows on banks and gravel bars in river and lake valleys, and on open grasslands and rocky slopes of mountains and cliffs. It has a circumboreal distribution. In the Flora region, it extends from Alaska across Canada to Newfoundland and Greenland, south in the mountains to Wyoming and Colorado in the west, and West Virginia, Tennessee, and North Carolina in the east. It also grows in arctic Europe, Scandinavia, the mountainous regions of Mexico, and northwestern South America, where some unusually robust specimens have been somewhat dubiously referred to this species. Agrostis mertensii is frequently confused with dwarf, awned forms of A. scabra (p. 646), but has larger spikelets, more culm nodes, larger anthers, slightly wider, flatter leaves, and panicles that are less expanded and less than lh the culm length. Agrostis mertensii is also often confused with A. idahoensis (p. 649), but A. mertensii tends to grow in better-drained habitats. Agrostis mertensii differs from A. anadyrensis (see next) in being less robust, having narrower, less abundant basal leaves, smaller panicles, and minor differences in the insertion of the awns on the lemmas. In addition, the panicle branches are smooth to weakly scabrous, contrasting with the branches of A. anadyrensis, which are strongly scabrous, with long acicules throughout their length. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The subfamily Pooideae includes approximately 3300 species, making it the largest subfamily in the Poaceae. It reaches its greatest diversity in cool temperate and boreal regions, extending across the tropics only in high mountains. The circumscription and relationships of tribes within the Pooideae are unsettled (see, for example, Catalan et al. 1997, 2004; Soreng and Davis 1998). In this flora, some previously recognized tribes have been combined with the Poeae. Recognition of some of these as subtribes is well supported; among these is the Hainardieae Greuter (which, at the subtribal level, is called the Parapholiinae Caro). Members of other traditional tribal groupings, such as the Aveneae Dumort., appear to be widely dispersed within the Poeae sensu lato. Further work will probably support the division of the expanded Poeae into additional tribes; there is as yet no clear indication as to what the boundaries of such tribes should be. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 24, p. 644. | FNA vol. 24, p. 57. | ||||||||||||||||||||||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Agrostis | Poaceae | ||||||||||||||||||||||||||||||||||||
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Synonyms | A. rupestris, A. mertensii subsp. borealis, A. borealis | |||||||||||||||||||||||||||||||||||||
Name authority | Trin. | Benth. | ||||||||||||||||||||||||||||||||||||
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