Monographs Details:
Authority:
Acevedo-RodrÃguez, Pedro & collaborators. 1996. Flora of St. John, U.S. Virgin Islands. Mem. New York Bot. Gard. 78: 1-581.
Acevedo-RodrÃguez, Pedro & collaborators. 1996. Flora of St. John, U.S. Virgin Islands. Mem. New York Bot. Gard. 78: 1-581.
Family:
Asteraceae
Asteraceae
Description:
Species Description - Erect annual herb 30-75 cm tall; stems much-branched, strigose and often scabrous throughout, conspicuously striate at least on younger parts. Leaves sessile above or lower ones with a winged petiole; upper stem leaves much reduced, lanceolate in outline, lower stem leaves with blades to 20 x 12 cm, ovate to oblong in outline, pinnatifid or bipinnatifid, the segments 2-6, paired, to 7 x 3 cm, linear or lanceolate, dentate or lobate. Inflorescence paniculate, with many small heads. Heads radiate; involucral bracts biseriate, the outer involucral bracts 5, separate, narrowly ovate, 1.5-2 mm long, acute, palea elliptic, ca. 1 mm long. Ray flowers inconspicuous; corollas cream-colored, persistent on achenes, the limb ca. 0.5 mm long, the tube obscure. Disk flowers many; corollas light yellow, ca. 1-2 mm long; ovary sterile; some outer flowers functionally male. Achenes flattened, 2 mm long; pappus of 2 broad awns 0.5 mm long; achenes falling in a complex of 1 ray achene (and the persistent corolla) and its subtending involucral bract and 2 disk flowers with their palea.
Species Description - Erect annual herb 30-75 cm tall; stems much-branched, strigose and often scabrous throughout, conspicuously striate at least on younger parts. Leaves sessile above or lower ones with a winged petiole; upper stem leaves much reduced, lanceolate in outline, lower stem leaves with blades to 20 x 12 cm, ovate to oblong in outline, pinnatifid or bipinnatifid, the segments 2-6, paired, to 7 x 3 cm, linear or lanceolate, dentate or lobate. Inflorescence paniculate, with many small heads. Heads radiate; involucral bracts biseriate, the outer involucral bracts 5, separate, narrowly ovate, 1.5-2 mm long, acute, palea elliptic, ca. 1 mm long. Ray flowers inconspicuous; corollas cream-colored, persistent on achenes, the limb ca. 0.5 mm long, the tube obscure. Disk flowers many; corollas light yellow, ca. 1-2 mm long; ovary sterile; some outer flowers functionally male. Achenes flattened, 2 mm long; pappus of 2 broad awns 0.5 mm long; achenes falling in a complex of 1 ray achene (and the persistent corolla) and its subtending involucral bract and 2 disk flowers with their palea.
Discussion:
Common names: false ragweed, feverfew, mule weed, quinine weed, whitehead broom.
Distribution:
Saint Croix Virgin Islands of the United States South America| Saint Thomas Virgin Islands of the United States South America| Tortola Virgin Islands South America| West Indies| Central America| South America|
Saint Croix Virgin Islands of the United States South America| Saint Thomas Virgin Islands of the United States South America| Tortola Virgin Islands South America| West Indies| Central America| South America|