Description from Flora of China
Cuscuta arvensis Beyrich ex Engelmann; C. arvensis var. calycina Engelmann; C. pentagona Engelmann var. calycina Engelmann; C. pentagona var. subulata Yuncker.
Stems yellowish green to yellow or orange, 0.5-0.8 mm in diam., smooth. Inflorescences lateral, usually compact globular clusters, 4-18-flowered, subsessile. Pedicel ca. 1 mm. Calyx cupular, enclosing corolla tube, ca. 1.5 mm; sepals 5, oval or circular, sometimes wider than long. Corolla white, short campanulate, ca. 2.5 mm, 4- or 5-lobed; lobes broadly triangular, apex acute or obtuse, often reflexed. Stamens shorter to longer than corolla lobes; anthers ovate, shorter than filaments; scales distinct, ovate, ca. as long as corolla tube, fimbrillate. Ovary globose. Styles 2; stigma globose. Capsule depressed globose, ca. 3 mm in diam., ca. 2 mm high, with withered corolla at base, irregularly opening. Seeds 1-4, often 3 or 4, dull yellow, ovoid. 2n = 56.
On Allium fistulosum Linnaeus. Fujian (Fuzhou Shi), Xinjiang [Africa, Asia, Australia, Europe, North America, Pacific Islands, South America].