Oxypolis rigidior (L.) Raf.

Oxypolis rigidior * (L.) Raf. Bull. Bot. Seringe 218. 1830
Sium rigidius L. Sp. PI. 251. 1753.
Oenanthe rigida Crantz, Class. Umbell. 85. 1767.
Sium longifolium Pursh, Fl. Am. Sept. 194. 1814.
Sium iricuspidatum Ell. Bot. S. C. & Ga. 1: 354. 1817.
Oenanthe ambigua Nutt. Gen. 1: 189. 1818.
Pastinaca rigida Spreng. in R. & S. Syst. Veg. 6: 586. 1820.
Pastinaca ambigua Torr. Fl. U. S. 315. 1824.
Oxypolis tricuspidata Raf. Bull. Bot. Seringe 218. 1830.
Archemora rigida DC. Prodr. 4: 188. 1830.
Archemora ambigua DC. Prodr. 4: 188. 1830.
Archemora tricuspidata DC. Prodr. 4: 188. 1830.
fThaspium tenuifolium Raf. Herb. Raf. 78. 1833.
Achemora serrala Raf. Herb. Raf. 78. 1833.
Pastinaca tricuspidata D. Dietr. Syn. PI. 2: 971. 1840.
Peucedanum rigidum Wood, Bot. & Fl. 136. 1870.
Peucedanum rigidius Baillon, Hist. PI. 7: 187. 1879.
Tiedemannia rigida Coult. & Rose, Bot. Gaz. 12: 74. 1887.
Tiedemannia rigida var. ambigua Coult. & Rose, Rev. N. Am. Umbell. 47. 1888.
Oxypolis rigidus Britton, Mem. Torrey Club 5: 239. 1894
Oxypolis rigidus var. longifolius Britton, Mem. Torrey Club 5: 239. 1894.
* As 0. rigida. Since "Sium rigidium Linn." is cited as synonym, this is interpreted as an orthographic error. Oxypolis longifolia Small, Fl. SE. U. S. 875. 1903.
Oxypolis rigidior var. ambigua B. L. Robinson, Rhodora 10: 35. 1908.
Oxypolis turgida Small, Man. SE. Fl. 986. 1933.
Plants 6-15 dm. high; leaves oval to deltoid in general outline, excluding the petioles 10-30 cm. long, 10-25 cm. broad, pinnate with 5-9 leaflets, the leaflets lanceolate or linear, 7-15 cm. long, 5-45 mm. broad, remotely salient-dentate or entire; petioles 5-10 cm. long; peduncles 6-30 cm. long; involucre of a few linear bracts 1-2 cm. long; involucel of a few linear bractlets 3-5 mm. long; rays 15-45, spreading, subequal, 3-12 cm. long; pedicels spreading, 5-15 mm. long; calyx-teeth conspicuous; fruit oval or oblong, 4-7 mm. long, 2.5-4 mm. broad.
Type locality: Virginia, Clayton.
Distribution: Wet ground along streams, bogs; New York and New Jersey to South Carolina, west to Minnesota and Texas (Demaree 16.078. Eggerl 6463. House 3064).