Agrostis L., Sp. Pl. 1: 61. 1753, nom. et typ. cons.

Vigosa-Mercado, J. Luis, Delgado-Salinas, Alfonso, Alvarado Cardenas, Leonardo O. & Eguiarte, Luis E., 2023, Revision of the genus Agrostis (Poaceae, Pooideae, Poeae) in Megamexico, PhytoKeys 230, pp. 157-256 : 157

Agrostis L., Sp. Pl. 1: 61. 1753, nom. et typ. cons.

= Vilfa Adans., Fam. Pl. 2: 495. 1763. Type: Agrostis. stolonifera L. (lectotype designated by Hitchcock (1920: 127)).

= Trichodium Michx., Fl. Bor.-Amer. 1: 41. 1803. Type: T. laxiflorum Michx. (lectotype designated by Hitchcock (1920: 127)).

= Agraulus P. Beauv., Ess. Agrostogr. 5, t. 4. 1812. Type: Agrostis canina L. (lectotype designated by Hitchcock (1920: 127)).

= Decandolia Bastard, Essai Fl. Maine et Loire 15, 28. 1809, nom. illeg. superfl. Type: Agrostis stolonifera L. (lectotype designated by Hitchcock (1937: 515)).

= Notonema Raf., Bull. Bot. (Geneva) 1: 220. 1830. Type: Agrostis arachnoides Elliott (= A. elliotiana Schult.).

= Bromidium Nees & Meyen, Nov. Actorum Acad. Caes. Leop.-Carol. Nat. Cur. 19, suppl. 1: 154. 1843. Type: Agrostis hygrometrica Nees (lectotype designted by Rúgolo 1982: 196)).

= Anomalotis Steud., Syn. Pl. Glumac. 1: 198. 1854. Type: A. quinqueseta Steud.

= Didymochaeta Steud., Syn. Pl. Glumac. 1: 185. 1854. Type: D. chilensis Steud. (lectotype designated by Clayton and Renvoize (1986: 134)).

= Chaetopogon Janch., Eur. Gatt. Farn. Bl.-Pfl. (ed. 2) 33. 1913. Type: not designated.

= Neoschischkinia Tzvelev, Bot. Zhurn. (Moscow & Leningrad) 53: 309. 1968. Type: Trichodium elegans Thore.

= Linkagrostis Romero Garcia & C. Morales, Candollea 42(1): 383. 1987. Type: Agrostis juressi Link.*

Type.

Agrostis canina L. (lectotype designated by Widén (1971: 13), see also Philipson (1937), Jarvis (1992) and commentary below).

Description.

Plants herbaceous, annuals or perennials, up to 1.2 m, caespitose, rhizomatous or stoloniferous, sometimes developing pseudoestolons. Tillers extravaginal and/or intravaginal. Culms decumbent to erect, usually slender, unbranched, internodes hollow. Leaves basal or cauline; sheaths open; auricles absent; ligules membranous, entire to lacerate, usually scabridulous dorsally; blades filiform to linear, flat, conduplicate, convolute, or involute. Synflorescence a panicle, usually terminal, contracted to open; branches usually in whorls. Spikelets up to 4.5 mm long, 1-flowered, pedicellate, laterally compressed; rachilla not prolonged beyond the base of the floret; disarticulation above the glumes; glumes as long as the spikelet, equal to unequal, keeled, membranous, usually 1-nerved, rarely awned; floret bisexual, shorter than the glumes, usually 1/3-3/4 the length of the glumes, rarely longer; callus rounded, glabrous to pubescent; lemmas rounded dorsally, apices entire, erose or toothed, membranous, (3)5-nerved, veins inconspicuous or prominent, unawned or awned dorsally, awn straight to geniculate; paleas often absent or diminute, sometimes well-developed and reaching (1/5-)1/3-3/4 of the lemma length; lodicules 2; anthers (1)3; ovary glabrous, styles 2, free to the base. Fruit a caryopsis; endosperm liquid, soft or solid. x= 7.

Commentaries.

The name Agrostis was first described in the work of Linnaeus, Genera Plantarum ( Linnaeus 1737: 19), with a Latin diagnosis. According to the International Code of Nomenclature for Algae , Fungi and Plants (Art. 13.1) ( Turland et al. 2018), the beginning of effective publication dates for generic names is 1st May 1753, with the publication of Species Plantarum ( Linnaeus 1753). In this latter work, Linnaeus described 12 names, classified in two groups: 1) Aristatae ( A. spica-venti L., A. miliacea L., A. arundinacea L., A. rubra L., A. canina L., A. paradoxa L.); and 2) Muticae ( A. stolonifera L., A. capillaris L., A. alba L., A. minima L., A. virginica L., A. indica L.). No type species was designated by Linnaeus.

Hitchcock (1905) designated A. alba as the type, but the original material of this name is a Poa L. species ( Widén, 1971), and the adoption of this name as lectotype would result in Agrostis becoming a synonym of Poa ( McNeill et al. 1987). Years later, Hitchcock (1920), proposed A. stolonifera as lectotype, but this name conflicts with the original description of the genus, since it mentions that the lemmas are awned ( Linnaeus 1737), and the original description of A. stolonifera mentions that the lemmas are unawned ( Linnaeus 1753).

Philipson (1937) was the first to propose as lectotype the name A. canina . Widén (1971) agreed with that choice, and formally designated this name, since it is the one that keeps better the usage of the generic name. Jarvis (1992) proposed the conservation of the name Agrostis , with a conserved type.

The species of this genus are often confused with other genera found in the study zone, with one-flowered spikelets, such as Lachnagrostis Trin., Muhlenbergia Scherb., Podagrostis (Griseb.) Scribn. & Merr., Polypogon Desf., Sporobolus R. Br., and some species of Peyritschia E. Fourn., but it is distinguished from them by the following combination of characters: spikelets disarticulating above the glumes, florets shorter than the glumes, usually 1/3-3/4 the length of the glumes, rarely longer, lemmas with usually five veins, dorsal awns often present, palea often reduced or absent (sometimes reaching up to 3/4 of the lemma length), and rachilla not prolonged. See the work of Sylvester et al. (2020b) for a key to differentiate Agrostis from morphologically similar genera.