生活型

herb

形態特徵

• Herbaceous annuals from an erect tap root. Stems 30–150(–200) cm tall, erect, unbranched at base, much branched apically, puberulous, glandular.
• Leaves alternate, cauline, initially forming a basal rosette but this wanting at anthesis, lanceolate and smaller upward, deeply pinnately dissected or bipinnatifid and larger toward base, to 18×10 cm, puberulous and glandular on both surfaces, petiolate. Inflorescences corymbose cymes, terminal and axillary, peduncle densely yellowish puberulous.
• Heads 3–5 mm across, numerous. Outer involucral bracts 5, narrowly ovate, acute, 2.1–2.5×1.2–1.4 mm, puberulous; inner bracts 5, obovate, thin, transparent, 1.5–1.8×2–2.2 mm wide, margins glandular, subtending a ray floret with 2 disc florets on either side. Ray florets 5, ligules white, ca. 0.5–0.7×0.5–1 mm, truncate to emarginate; style branches linear, smooth, slightly exserted; pappus of 2 scales, whitish green, obovate, ca. 0.5 mm long; corolla whitish green, 4-lobed, lobes acute; stamens 4, white, ca. 1.1–1.3 mm long; pollen white; ovary rudimentary. Paleae oblanceolate, ca. 1.5×0.8 mm, thin, margins glandular, enclosing disc floret.
• Achenes black, narrowly obovate, ca. 2×1.1–1.4 mm, sparsely glandular, crowned by 1 persistent ligule and 2 pappus scales, fused at base to 2 adjacent sterile disc florets.
• Chromosome number, n = 17 (Peng, Hu & Kao, 1988).

分布

• 台灣 : widely naturalized on open seashores and in lowland waste places throughout the island.
• 世界 : The southern United States, Mexico, Honduras, the West Indies and South America; widely adventive in subtropical areas of the Old World.

引證標本

TAIPEI: Nankang, Academia Sinica, Peng 11542. KAOHSIUNG: Kaohsiung City, Yang 3992; Liukuei, Yen 1745.

參考文獻

• PENG, Ching-I & CHUNG, Kuo-Fang; LI, Hui-Lin, Flora of Taiwan, second edition 4: 1026. 1998.  (Fl. Taiwan 2nd edit.)