Ambrosia 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 : 142

49. Ambrosia L. 1

Annual or perennial herbs. Leaves mostly opposite. Capitula unisexual, inconspicuous; male hemispherical, drooping, in terminal, ebracteate racemes; female in axils of the uppermost leaves, each with a single floret. All florets tubular. Achene enclosed by the nut-like involucre; pappus absent; involucre usually with small spines or tubercles near apex.

Literature: A. Lawalrée, Bull. Jard. Bot. Bruxelles 18: 305-315 (1947); Bull. Soc. Bot. Belg. 87: 207-208 (1955). E.-J. Bonnot, Bull. Mens. Soc. Linn. Lyon 36: 348-359 (1967).

1 Leaves palmately 3- to 5-lobed or entire, all opposite; involucre

6-10 mm in fruit 5. trifida 1 Leaves pinnatifid, sometimes alternate; involucre 3-5 mm in fruit

2 Perennial; involucre in fruit unarmed or with short, blunt

teeth 4. coronopifolia 2 Annual; involucre in fruit with 4-7 acute, spinose teeth or conical tubercles

3 Plant aromatic; involucre in fruit 5-angled, glandularpubescent, with 5 conical tubercles; beak 0-5 mm

1. maritima 3 Plant not aromatic; involucre in fruit fusiform-obovoid, weakly angled, wrinkled, ±glabrous, with spinose teeth; beak 1-1-5 mm

4 Female capitula in clusters of 2-4 2. artemisiifolia 4 Female capitula solitary 3. tenuifolia