Arracacia ternata Mathias & Constance

Arracacia ternata Math. & Const. Bull. Torrey Club 68: 254. 1941.
Slender, caulescent, branching from a stout, horizontal woody root, 6-10 dm. high, glabrous throughout or the foliage minutely scaberulous; leaves deltoid in general outline, excluding the petioles 1.5-3 dm. long, 3-4-ternate, the leaflets ovate-lanceolate, acute at the apex, cuneate at the base, all but the terminal distinct, petiolulate or sessile, 2-5 cm. long, 1-2 cm. broad, coarsely toothed and lobed with triangular mucronate teeth; petioles very slender, 5-15 cm. long, sheathing at the base; cauline leaves few, like the basal, the uppermost greatly reduced and consisting of 1-several elongate, filiform lobes 1-2 cm. long, the sheaths obsolete; inflorescence freely branched, the lower peduncles alternate, the upper verticillate, slender, 3-6 cm. long, often with a small sterile lateral umbel; involucre wanting, or of a solitary foliaceous linear bract; involucel of 1-several linear bractlets, 3-5 mm. long, exceeding the flowers; fertile rays 5-6, slender, spreading-ascending, subequal, 2-3.5 cm. long; fertile pedicels 1-5, slender, spreading-ascending, 3-6 mm. long; flowers purple, the petals oval; stylopodium low-conic, with a conspicuous crenulated disk, the styles short, divergent or recurved; carpophore 2-cleft to the base; fruit oblong, 7-12 mm. long, 2-3 mm. broad, glabrous, tapering at each end, and with a V-shaped notch at the apex, the ribs filiform; oil-tubes small, 1 or 2 in the intervals, 4 on the commissure; seed-face deeply sulcate.
Type locality: Cerro Parrena, vicinity of San Jose, Sierra de San Carlos, Tamaulipas, Bartlell 10,294.
Distribution: Known only from the type locality.