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(Last Modified On 6/4/2013)
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(Last Modified On 6/4/2013)
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Species
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Ageratum conyzoides L.
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PlaceOfPublication
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Sp. P1. 2: 839. 1753.
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Note
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TYPE: America (Herb. Linn. 979.1 or 979.2, not seen, US, microfiche).
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Synonym
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Ageratum hirtum Lam., Encycl. Meth. 1: 54. 1783. TYPE: Cape of Good Hope, Sonnerat (P, not seen, US, microfiche). Ageratum humile Salisb., Prodr. Stirp. 188. 1796. TYPE: England, Chapel Allerton, Salisbury? (K?, BM?, not seen). Ageratum hirsutum Lam. in Poiret, Encycl. Meth. Bot. Suppl. 1: 242. 1810. TYPE: Lamarck, Illust. tab. 672, fig. 2. Ageratum album Willd. ex Steud., Nom. Bot., ed. 1. 18. 1821, nom. nud. Cacalia mentrasto Vell., Fl. Flum. 339. 1825. TYPE: Vellozo, Fl. Flum. 8, tab. 69. 1831. Vellozo types at the "Cabinet d'Histoire naturelle de Rio de Janeiro" not known to exist. Ageratum cordifolium Roxb., Fl. Ind. 3: 415. 1832. TYPE: India, Bengal, perhaps Wallich Cat. 3177/287 (K, not seen; G, not seen, US, microfiche).
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Description
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Annual or short-lived perennial erect herbs or subshrubs to 1.5 m tall, sparingly branched; stems becoming brownish to slightly reddish, terete, slightly striate, usually fistulose, sparsely to densely long-pilose, usually also slightly puberulous. Leaves mostly opposite; blades ovate to broadly ovate, to 10 cm long and 7 cm wide, the base rounded to cuneate, strongly trinervate from the base, the margins usually crenate, the apex short-acute to narrowly rounded or obtuse, the upper sur- face dull green, sparsely long-pilose, the lower surface slightly paler green, promi- nently glandular-punctate, sparsely pilose on the veins and veinlets; petioles to 2.5 mm long. Inflorescence cymose to subcymose with compact corymbose to sub- umbellate branches, the branches somewhat densely puberulous with few to many longer hairs, the ultimate branches 3-10 mm long, often slightly enlarged distally. Heads ca. 4.0-4.5 mm high with ca. 50 florets; involucral bracts 25-30, eximbricate, in 2 series, mostly 3-4 mm long, oblong-lanceolate, prominently bicostate, with prominent antrorsely angular or lacerate scarious margins, the apex shortly to very sharply acute, usually not scarious near tip, the outer surface with usually few long hairs; receptacle naked; corolla white or blue, ca. 1.7 mm long, narrowly funnelform, with few hairs on the outer surface, the tube narrow, ca. 1 mm long, with scattered small short-stalked glands, the lobes 0.2-0.3 mm long, with papillae moderately developed inside, at tip and on margins, 1-2 hairs on outer surface; style branches extremely slender, sometimes short, with crowded blunt papillae
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Habit
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herbs or subshrubs
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Description
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forming nearly 1/2 the width. Achenes ca. 1.2 mm long, with sparse short bristles usually restricted to the ribs; carpopodium asymmetrical; pappus of 5 large free scales, the scales usually lanceolate with long slender awns, to 2 mm long with awns.
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Distribution
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native in Central and South America and has become widely adventive in most tropical and many subtropical parts of the world.
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Note
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The species has been confused with A. houstonianum and differences are discussed under that species. The recent monograph by Johnson (1971) noted the unreliability of the pappus structure in this species and reduced to synonymy the species A. latifolium Cav., having awnless pappus scales. This latter species has been omitted from the present synonymy as further studies are required. Use of other characters such as corolla size and style branch structure show that some of the awnless material probably is A. conyzoides and some is A. houstoni- anum and still other material does not seem to be obviously either of these.
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Specimen
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BOCAS DEL TORO: Changuinola, Lazor et al. 2380 (FSU). Bocas del Toro, Lazor et al. 2413 (FSU). SW of Bocas del Toro at Maccaw Hills, Isla Colon, 0-120 m, von Wedel 427 (MO). Isla Col6n, von Wedel 2931 (MO, US). CANAL ZONE: Balboa, Macbride & Featherstone 31 (F, US). Near Gatu'n, Standley 27309 (US). Vic. of Summit, Standley 30089 (US). CHIRIQI: Boquete Lookout, 4000 ft, D'Arcy & D'Arcy 6324 (MO). Boquete, D'Arcy & D'Arcy 6349 (MO). Concepcion, King 5286 (US). Alto Boquete, 1125 m, Partch 69-90 (MO). Vic. of San FMix, 0-120 m, Pittier 5432 (US). COCLE: El Valle, Dwyer 1839 (FSU, MO, US); King 5327 (US). El Valle de Anton and vic., 500-700 m, Seibert 473 (MO). DARIEN: Puerto St. Dorotea, Dwyer 2227 (MO). PANAMA: Isla Taboga, 0-350, m, Allen 1277 (F, MO). 7 mi N of Cerro Azul on road to Ceriro Jefe, 2600 ft, Blum et al. 1757 (FSU). Cerro Campana, Croat 12097 (MO). Cerro Azul, 2000 ft, D'Arcy & D'Arcy 6217 (MO). Goofy Lake to ca. 8 mi S of Goofy Lake toward Cerro Jefe, Dwyer 7055 (MO). SW facing slopes of Cerro Azul, King 5248 (US). Cerro Campana, Lazor 3324 (FSU). Altos del Rio Pacora, 2500 ft, Lewis et al. 2283 (MO). Chimaln, Lewis et al. 3366 (MO, UC). Taboga Island, Longfield 488 (US); Standley 27975 (US). Cerro Azul, 2000 ft, Tyson 2057 (FSU), 2059A (MO); ca. 2200 ft, Tyson 6285 (FSU, MO, US); 2100 ft, Tyson 6320 (FSU, MO). Cerro Jefe, Tyson et al. 4298 (FSU, MO).
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