(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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Brickellia diffusa (Vahl) A. Gray
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PlaceOfPublication
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PI. Wright. 1: 86. 1852.
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Synonym
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Eupatorium diffusum Vahl, Symb. Bot. 3: 94. 1794. TYPE: South America, Forsskall (C, not seen). Bulbostylis diffusa (Vahl) DC., Prodr. 7: 268. 1838. Eupatorium trichosanthum A. Rich. in R. de la Sagra, Fl. Cub., Fanerog. 3: 41. 1853. TYPE: Cuba, Jagua, Ossa (P, not seen). Coleosanthus diffusus (Vahl) Kuntze, Rev. Gen. PI. 1: 328. 1891.
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Description
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Erect sparingly branched annual herb to 2 m tall; stems yellowish to slightly reddish, terete, scarcely striate, glabrous. Leaves opposite; blades deltoid to broadly ovate, to 10 cm long and 11 cm wide, the base broadly rounded to truncate, prominently acuminate and trinervate, the margins closely serrate-dentate, the apex shortly and abruptly apiculate, the upper surface with sparse short coarse pubescence, the lower surface densely covered with numerous oblong or reniform glands; petioles slender, to 6 cm long. Inflorescence a lax profusely branching elongate panicle with paniculate branches, the ultimate branches 4-20 mm long, glabrous. Heads ca. 7 mm high, slender, with mostly 8-14 florets; involucral bracts ca. 20, subimbricate, in 3-4 series, lanceolate to linear-lanceolate, 1-7 mm long, the apex sharply acute, the margins scarious, the outer surface bicostate, glabrous; corolla whitish, 4-5 mm long, slender, narrower above, glabrous except for a few glands on the lobes, the lobes minute; style branches filiform, tapering to the tip. Achenes 1.5-2.0 mm long, densely covered with small bristles; carpopodium prominent; pappus of 30-40 bristles with minutely scabrellous margins. Pollen mostly 20-25 microns in diameter, micropapillose.
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Habit
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herb
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Note
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The species is both the most widely distributed and most atypical member of the genus Brickellia.
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Distribution
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restricted to the western United States, Mexico, and Central America, but B. diffusa occurs in Mexico southward to Peru and Brazil and also in the Greater Antilles.
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Note
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The genus and its relatives are generally characterized by the very broadly clavate style branches, but B. diffusa has filiform style branches with stigmatic lines sometimes reaching very near the tip. The species does retain most of the characteristic features of Brickellia including the appressed involucral bracts, the constricted corolla, the large and prominently tomentose style node, the ten-ribbed achene, and the flattened outer surfaces of the pappus bristles.
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Specimen
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CANAL ZONE: Chiva-Chiva trail, Red tank to Pueblo Nuevo, Piper 5741 (US). Balboa, Standley 29298 (US)-.-CHIRIQUI: Distrito Guanabano, Quebrada Guanabano, 0-100 m, Croat 22502 (MO). Quebrada Merida, 4 mi S of Puerto Armuelles, 0-100 m, Liesner 383 (MO). Monte Verde, 2.5 km W of Puerto Armuelles, 80 m, Liesner 59 (MO). DARIEN: Isla Pedro Gonzales, Duke 10396 (MO, OS). Above Paca, R. S. Williams 710 (US). PANAMA': Juan Diaz, Standley 30631 (US). Nuevo San Francisco, Standley 30717 (MO, US).
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