Lachnagrostis filiformis |
Poaceae |
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Pacific bent |
grass family |
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Habit | Plants perennial; cespitose, sometimes rhizomatous. | Plants annual or perennial; usually terrestrial, sometimes aquatic; tufted, mat-forming, cespitose, pluricespitose, or with solitary culms (flowering stems), rhizomes and stolons often well developed. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Culms | 15-65 cm, erect, sometimes geniculate basally. |
annual or perennial, herbaceous or woody, usually erect or ascending, sometimes prostrate or decumbent for much of their length, occasionally climbing, rarely floating; nodes prominent, sometimes concealed by the leaf sheaths; internodes hollow or solid, bases meristematic; branching from the basal nodes only or from the basal, middle, and upper nodes; basal branching extravaginal or intravaginal; branching from the upper nodes intravaginal, extravaginal, or infravaginal. |
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Sheaths | glabrous, sometimes scabridulous; ligules 2.2-7.8 mm, obtuse or acute, lacerate; blades 8-20 cm long, 1-3 mm wide, usually flat, sometimes involute, finely scabrous. |
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Leaves | alternate, 2-ranked, each composed of a sheath and blade encircling the culm or branch; sheaths usually open, sometimes closed, the margins fused for all or part of their length; auricles (lobes of tissue extending beyond the margins of the sheaths on either side) sometimes present; ligules usually present at the sheath-blade junction, particularly on the adaxial surface, abaxial ligules common in the Bambusoideae, membranous, sometimes ciliate, adaxial ligules usually present, of membranous to hyaline tissue, a line of hairs, or a ciliate membrane; blades usually linear to lanceolate, occasionally ovate to triangular, bases sometimes pseudopetiolate (having a petiole-like constriction), venation usually parallel, sometimes with evident cross veins, occasionally divergent. |
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Panicles | 7-30 cm long, (2)5-25 cm wide, broadly ovate, loose and diffuse at maturity, bases sometimes not exserted at maturity; branches capillary, scabrous, often deflexed at maturity, branched above the middle, spikelets confined to the distal 1/3; lower branches 5-15 cm; pedicels 0.5-7 mm; disarticulation above the glumes and below the panicles. |
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Inflorescences | (synflorescences) usually compound, composed of simple or complex aggregations of primary inflorescences, aggregations paniculate, spicate, or racemose or of spikelike branches, often with an evident rachis (central axis), primary inflorescences spikelets, pseudospikelets, or spikelet equivalents; inflorescence branches usually without obvious bracts. |
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Spikelets | greenish to yellowish, often tinged with purple; rachilla prolongations about 1 mm, bristlelike, pilose distally, hairs about 0.6 mm. |
with (0-1)2(3-6) glumes (empty bracts) subtending 1-60 florets, glumes and florets distichously attached to a rachilla (central axis); pseudospikelets with bud-subtending bracts below the glumes. |
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Glumes | equal to subequal, 2.8-3.6 mm, scabrous on the midvein, at least distally, 1(3)-veined, apices long-acuminate; callus hairs to 0.5 mm, abundant; lemmas 1.8-2.3 mm, translucent to opaque, usually densely hairy at least on the lower 1/2, hairs to 0.7 mm, 5-veined, apices truncate to obtuse, erose or 2-4-toothed, awned from the middle 1/3 of the lemmas, awns 4-7.5 mm, geniculate; paleas (0.4)1.2-1.5 mm, usually more than 2/3 the length of the lemmas, thin, veins usually not visible; anthers 3, about 0.5 mm. |
usually with an odd number of veins, sometimes awned. |
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Caryopses | about 1.2 mm; endosperm solid. |
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Florets | bisexual, staminate, or pistillate, usually composed of a lemma (lower bract) and palea (upper bract), lodicules, and reproductive organs, often laterally or dorsally compressed, sometimes round in cross section; lemmas usually with an odd number of veins, often awned, bases frequently thick and hard, forming a callus, backs rounded or keeled over the midvein, awns usually 1(-3), arising basally to terminally; paleas usually with 2 major veins, with 0 to many additional veins between the major veins, sometimes also in the margins, often keeled over the major veins; lodicules (0)2-3, inconspicuous, usually without veins, bases swelling at anthesis; stamens usually 3, sometimes 1(2) or 6+, filaments capillary, anthers versatile, usually all alike within a floret, sometimes 1 or 2 evidently longer than the others; ovaries 1-loculed, with (1)2-3(4) styles or style branches, stigmatic region usually plumose. |
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Fruits | caryopses, pericarp usually dry and adhering to the seed, sometimes fleshy or dry and separating from the seed at maturity or when moistened; embryos ⅕ as long as to almost equaling the caryopses, highly differentiated with a scutellum (absorptive organ), a shoot with leaf primordium covered by the coleoptile (shoot sheath), and a root covered by the coleorhiza (root sheath); hila punctate to linear. |
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x | = 5,6, 7, 9, 10, 11, 12. |
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2n | = 56. |
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Lachnagrostis filiformis |
Poaceae |
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Distribution | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Discussion | Lachnagrostis filiformis is native to New Guinea, Australia, New Zealand, and Easter Island. In North America, it grows in open, disturbed sites such as roadsides and burned areas, and has been spreading into vernal pools around San Diego, California. It was introduced to North America in the late nineteenth century, but is only known to be established in California. The most recent record located for Texas was collected in 1902. Records from South Carolina are from "waste areas around wool-combing mill; rare, perhaps only a waif." (Weakley, http: //www. herbarium.unc/ edu/flora.htm). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The Poaceae or grass family includes approximately 700 genera and 11,000 species (Chen et al. 2006). The two grass volumes in this series treat 10 subfamilies, 25 tribes, 236 genera, and 1373 species. Of these, all the subfamilies, 22 tribes, 136 genera, and 892 species are native to the Flora region; 2 tribes, 78 genera, and 290 species have become established in the region. The remaining taxa include ornamental species; species grown for research purposes; species that, if introduced to the region, would pose a threat to important agricultural species; and a few waifs, i.e., species that have been found in the region but have not become established. Most of the waifs are species that were found on ballast dumps near ports around the turn of the last century. Grasses constitute the fourth largest plant family in terms of number of species. Nevertheless, the family is clearly more significant than any other plant family in terms of geographic, ecological, and economic importance. Grasses grow in almost all terrestrial environments, including dense forests, open deserts, and freshwater streams and lakes. There are no truly marine grasses, but some species grow within reach of the highest tides. In addition to being widely distributed, grasses are often dominant or co-dominant over large areas. The importance of such areas to humans is reflected in the many words that exist for grasslands, words such as meadow, palouse, pampas, prairie, savanna(h), steppe, and veldt. Not surprisingly, given their abundance and prevalence, grasses are of great ecological importance as soil stabilizers and as providers of shelter and food for many different animals. The economic importance of grasses to humans is almost impossible to overestimate. The wealth of individuals and countries is dependent on the availability of such sources of grain as Triticum (wheat), Oryza (rice), Zea (corn or maize), Hordeum (barley), Avena (oats), Secale (rye), Eragrostis (tef), and Zizania (wild rice). Most countries invest heavily in research programs designed to develop better strains of these grasses and the many other grasses that are used for livestock, soil stabilization, and revegetation. Developing improved grasses for recreation areas, such as playing fields, golf courses, and parks, is also a major industry in many parts of the world; increasing recognition of the aesthetic value af grasses is reflected in their prominence in horticultural catalogs. There are, of course, grasses that are considered undesirable, at least in some parts of the world, but even the most obnoxious grasses may be well-regarded over a portion of their range. For instance, Bromus tectorum (cheatgrass) is a noxious, fire-prone invader of western North American ecosystems; it is also welcomed as a source of early spring feed in some parts of the Flora region. Cynodon dactylon (bermudagrass) is listed as a noxious weed in some jurisdictions; in others it is valued as a lawn grass. Although grasses are widespread and often dominant in open areas, all evidence points to an origin of the family in forests, most likely in the Southern Hemisphere, at least 55-70 mya (Grass Phylogeny Working Group 2001). Recent evidence from phytoliths (isolated silica bodies commonly produced inside the epidermal cells of grasses and some other plants) embedded in fossil coprolites strongly suggests that grasses evolved earlier in the Cretaceous than previously thought (Prasad et al. 2005). Living representatives of the three earliest lineages of the grass family, together comprising about 30 species, are perennial, broad-leaved plants of relatively small stature, native to tropical or subtropical forests in South America, Africa, southeast Asia, some Pacific Islands, and northern Australia. The major diversification of the family probably occurred in the mid-Cenozoic, and was associated with climatic changes that produced more open habitats. All major lineages of the grass family were present by the middle of the Miocene (Jacobs et al. 1999), and C4 photosynthesis in grasses had evolved by then, as well. Molecular and morphological data unequivocally support a single origin for the Poaceae (Grass Phylogeny Working Group 2001). The caryopsis, a single-seeded, usually dry and indehiscent fruit with the pericarp usually strongly adherent to the seed, and the laterally positioned, highly differentiated embryo are unique to grasses. Beyond the three early-diverging lineages (Anomochlooideae Potztal, Pharoideae, and Puelioideae L.G. Clark et al.), the great diversity of grasses can be divided into two major lineages: the BEP clade (Bambusoideae, Ehrhartoideae, and Pooideae); and the PACMCAD clade (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae Pilger, Centothecoideae, Aristidoideae, and Danthonioideae, i.e., the PACCAD clade of volume 25 plus the Micrairoideae, support for recognition of which was obtained after publication of that volume). Relationships among the BEP grass lineages remain uncertain, and some evidence points to the Pooideae as being more closely related to the PACMCAD clade than to the Bambusoideae or Ehrhartoideae. The PACMCAD clade includes all known C4 or warm-season grasses. The closest relatives of the Poaceae lie within a group of six families, all native primarily to the Southern Hemisphere: Joinvilleaceae Toml. & A.C. Sm., Ecdeiocoleaceae D.F. Cutler &c& Airy Shaw, Restionaceae R. Br., Centrolepidaceae Endl., Anarthriaceae D.E Cutler &c& Airy Shaw, and Flagellariaceae Dumort. (Poales Small, sensu stricto). Joinvilleaceae, Ecdeiocoleaceae, and Poaceae constitute a three family clade, with Ecdeiocoleaceae probably being closer than Joinvilleaceae to the Poaceae (Bremer 2000; Bremer 2002; Michelangeli et al. 2003). Rudall et al. (2005), based on a study of reproductive structures in the Ecdeiocoleaceae, suggest that the grass caryopsis may represent "one end of a transformation series embodied by the reduced gynoecial structure and indehiscent fruit of other Poales such as Flagellaria and Ecdeiocolea" (p. 1441). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key | Key to Tribes
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Source | FNA vol. 24, p. 696. | FNA vol. 24, p. 3. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Poaceae > subfam. Pooideae > tribe Poeae > Lachnagrostis | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Synonyms | Agrostis retrofracta, Agrostis avenacea | family gramineae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (G. Forst.) Trin. | Barnhart | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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