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Project Name Data (Last Modified On 6/4/2013)
 

Flora Data (Last Modified On 6/4/2013)
Genus Ageratina Spach
PlaceOfPublication Hist. Veg. Phan. 10: 286. 1841.
Note TYPE: Eupatorium aromaticum L.
Synonym Batschia Moench, Meth. 567. 1794, not Batschia Gmelin, 1791 (Boraginaceae); nor Batschia Mutis ex Thunb., 1792 (Menispermaceae); nor Batschia Vahl, 1794 (Leguminosae) . TYPE: Batschia nivea Moench = Eupatorium ageratoides L.f. Ageratiopsis Schultz-Bip. ex Benth. & Hook., Gen. P1. 2: 246. 1873, nom. nud. TYPE: Eupatorium ageratoides L.f. Mallinoa Coult., Bot. Gaz. (Crawfordsville) 20: 47. 1895. TYPE: M. corymbosa Coult. Kyrstenia Neck. ex E. L. Greene, Leafl. Bot. Observ. Crit. 1: 8. 1903. TYPE: Eupatorium aromaticum L.
Description Sparingly to densely branched perennial herbs or shrubs. Leaves usually opposite, rarely subopposite or alternate, short- to long-petiolate; blade deltoid to narrowly elliptical, toothed or lobed to entire, serrate in most species. Inflores- cence laxly to densely corymbose. Heads discoid with 10-60 florets; involucre of ca. 30 rather narrow usually acute subimbricate bracts in 2-3 series, spreading at maturity; receptacle glabrous or with minute scattered hairs, usually slightly convex; corolla with a broad to very narrow basal tube and a narrowly to broadly campanulate limb, the lobes 5, slightly to distinctly longer than wide, densely papillose on the inner surface, smooth with glands or hairs on the outer surface, the cells of the limb mostly narrow with sinuous walls; anther collars mostly narrow, with many quadrate cells below, elongate cells above, the walls with little or no ornate thickening, the exothecial cells in the outer valve usually longer than wide, the anther appendage large, longer than wide; style usually with distinct basal enlargement, glabrous, the style appendages usually densely long-papillose. Achenes prismatic or often fusiform, usually 5-ribbed, usually with bristles or glands or both; carpopodium distinct without a distinct upper rim, short- to long- cylindrical, the cells moderately large quadrate to oblong in many series with thin and beaded walls; pappus of 5-40 slender scabrous usually easily deciduous bristles, the zone of basal cells often fragile, the apices often enlarged, the apical cells acute. Pollen with short spines, often deformed and nonfunctional.
Habit herbs or shrubs
Distribution Ageratina is a large genus of approximately 230 species ranging from the eastern United States to Mexico, Central America, the West Indies, and western South America.
Note Two species, A. adenophora (Spreng.) R. M. King & H. Robinson and A. riparia (Regel) R. M. King & H. Robinson, have become widely adventive in warmer parts of the Old World. Seven species have been collected in Panama. Ageratina and a number of related genera such as Oxylobus form a distinct element in the tribe that is cytologically notable for its base numbers of x= 17 and x = 16 (King & Robinson, 1970, 1972).
Reference King, R. M. & H. Robinson. 1970. Studies in the Eupatorieae (Compositae). XIX. New combinations in Ageratina. Phytologia 19: 208-229. king & robinson. 1972. Studies in the Eupatorieae (Asteraceae). LXXXV. Additions to the genus Ageratina with a key to the Costa Rican species. Phytologia 24: 79-104. King & Robinson. 1974. Studies in the Eupatorieae (Asteraceae). CXXVIII. Four additions to the genus Ageratina from Mexico and Central America. Phytologia 28: 494-502.
Key a. Corolla with short-stalked glands on outer surface, without hairs; involucral bracts without distinct striations; pappus spreading with age, not fragile at base ...... 1. A. anisochroma aa. Corolla without distinct glands on outer surface, with few to many hairs; involucral bracts bicostate; pappus fragile at base and easily deciduous. b. Involucral bracts with glands on outer surface, with few or no hairs. c. Leaves subsessile, petioles ca. 1 mm long; involucral bracts obtuse to sharply acute ...... 3. A. chiriquensis cc. Leaves distinctly petiolate, petioles mostly 1-4 cm long; involucral bracts with attenuate tips ...... 5. A. ixiocladon bb. Involucral bracts without glands on outer surface, with many hairs. d. Leaves with narrowly acuminate tips; heads with 10-15 florets ......  4. A. croatii dd. Leaves with tips obtuse to acute, not or scarcely acuminate; heads with 19-55 florets. e. Leaves membranaceous; corolla tube distinctly longer than limb; inflorescence not densely branched ...... 6. A. molinae ee. Leaves papyraceous; corolla tube about as long as limb or shorter; inflores- cence compactly corymbosely branched. f. Leaf blades with cuneate bases, lower surface sparsely puberulous; heads with 19-28 florets; involucral bracts with only narrow scarious margins ....... 7. A. whitei ff. Leaf blades with rounded to slightly cordate bases, lower surface often densely hirtellous; heads with 25-55 florets; inner involucral bracts with broad scarious margins ...... 2. A. aschenborniana
 
 
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