2. Cuscuta cephalanthi Engelm. (buttonbush dodder)

Pl. 365 d–f; Map 1584

Stems relatively slender, usually less than 1 mm in diameter. Flowers 2.0–2.5 mm long, with smooth to slightly irregular surfaces, subtended by at most 1 lanceolate to ovate bract (usually none), in spikelike or cymose clusters on short side branches, the pedicels absent or very short. Calyces about 1/2 as long as the corolla tube, 3- or 4-lobed 1/2–2/3 of the way to the base, the lobes ovate, rounded at the tip, not or slightly overlapping basally, not angled. Corollas with 3 or 4 rounded lobes, these erect to spreading, with incurved tips. Infrastaminal scales usually not quite reaching filament bases, narrowly oblong, deeply toothed to fringed along the margins. Fruits globose to depressed-globose, the wall not thickened at the tip. Seeds 1.5–2.0 mm long. 2n=60. July–September.

Scattered nearly throughout the state (U.S., Canada). Stream banks, bottomland forests, and wet prairies. Parasitic on both herbaceous and woody host species, including species of Aster, Boehmeria, Cephalanthus, Cynanchum, Eupatorium, Justicia, Lycopus, Lysimachia, Polygonum, Salix, Saururus, and Vernonia.

In this species, frequently only 1 or 2 seeds mature in each fruit, giving the capsules a somewhat lopsided appearance. The papery remains of the corollas frequently cap the fruits.