Bidens tripartita, L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1976, Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae), Cambridge University Press : 140

1. B. tripartita L. , Sp. Pl. 831 (1753)

(incl. B. bullata L. , В. orientalis Velen. ).

Almost glabrous to hirsute annual (3-)10- 60(-100) cm. Leaves usually 3-lobed, less frequently 5-lobed or unlobed, coarsely serrate; petiole short, winged. Capitula 10-25 mm in diameter, wider than long; outer involucral bracts 5-8, usually leaf-like, the inner ovate, brownish with a green margin. Receptacular scales as long as the achenes, oblong-lanceolate, scarious, with dark lines. Achenes (4-)5-6 mm, cuneiform; marginal setae deflexed; bristles (2)3-4. 2zz = 48. Damp places. Most of Europe, but rare in the extreme north and extreme south. All except Az BI Cr Fa Is Sb.

Very variable in size, dissection of leaves and length of outer involucral bracts. Much of the variation appears to depend on time of germination and edaphic factors, but a single plant can exhibit considerable variation.