Ptilimnium capillaceum (Michx.) Raf.

Ptilimnium capillaceum (Michx.) Raf. Bull. Bot Seringe 1: 217. 1830.
Ammimajus ? Walt. Fl. Car. 113. 1788. Not A . majus L. 1753. Ammi capillaceum Michx. Fl. Bor. Am. 1: 164. 1803. Ammi rubricaule Hornem. Hort. Hafn. 272. 1813. Ammi junceum Raf. Neog. 1: 2. 1825. (Nomen nudum.) Discopleura capillacea DC. Coll. Mem. S: 38. 1829. Ptilimnium junceum Raf. Bull. Bot. Seringe 217. 1830. Aethusa capillacea Nutt.; DC. Prodr. 4: 106, as syn. 1830. Discopleura juncea Steud. Nom. Bot. ed. 2. 1: 520. 1840. Discopleura major B. S. P. Prel. Cat. 22. 1888.
Plants 1-S.5 dm. high; leaves verticillate at the nodes, polymorphic in submerged forms, broadly oblong in general outline, excluding the petioles 5-13 cm. long, 2-4 cm. broad, pinnately decompound, the ultimate divisions filiform, 5-30 mm. long, 0.25-1 mm. broad; petioles obsolete to 1.5 cm. long, entirely winged-sheathing; peduncles 2.5-10.5 cm. long, exceeding the leaves; involucre of several pinnately cleft or rarely entire bracts about one-half as long as the rays; involucel of filiform entire bractlets shorter than the pedicels; rays 4—20, spreading, subequal, 1-3.5 cm. long; pedicels 5-20, 3-12 (usually 4—6) mm. long; petals acute; calyx-teeth small, deltoid, persistent; anthers purple; styles short, about equaling the stylopodium; fruit broadly ovoid, 1.5-3 mm. long, 1.5-2 mm. broad, the lateral ribs conspicuous.
Type locality: "In campestribus Carolinae," collector unknown.
Distribution: Massachusetts to Florida, west to Missouri, Kansas, and Texas (Curtiss 4341,

Ptilimnium capillaceum, known by the common name of herbwilliam, is a member of the carrot family, Apiaceae. It is a perennial herb, native to the eastern United States, from Texas to Massachusetts.