1. Torilis arvensis (Huds.) Link (field hedge-parsley, hemlock chervil)

Pl. 214 c–e; Map 889

Stems 20–100 cm long, usually relatively slender. Inflorescences terminal and sometimes also axillary, consisting of noticeably compound umbels, these short- to long-stalked. Involucre absent or of 1(2) bract(s), the bract(s) 1–12 mm long, narrowly triangular to more commonly linear, often hairlike. Rays 3–10, 0.5–2.5 cm long. Flower stalks 1–4 mm long, the umbellets thus often appearing dense and headlike. Fruits 3–5 mm long, the bristles all elongate, 0.6–1.1 mm long, about as long as the width of the body of the mericarp, spreading at nearly 90° from the fruit and straight or slightly arched. 2n=12. June–September.

Introduced, scattered to common throughout the state (native of Europe, Asia; widely introduced in the eastern U.S. west to Wisconsin and Texas, and disjunctly California and Oregon; also Canada, Caribbean Islands, and South America). Banks of streams and rivers, disturbed portions of glades, upland prairies, and savannas, and regenerating clear-cuts in mesic upland forests; also roadsides, railroads, old fields, and open, disturbed areas.

Steyermark (1963) and many earlier authors mistakenly treated this species under the name T. japonica, in spite of the detailed descriptions and key provided by Mathias and Constance (1944–1945), who themselves apparently reversed the distributional range statements of the two taxa. Mühlenbach (1979) was the first to note the problems with older treatments.

Torilis arvensis has become much more abundant in Missouri during recent decades. Steyermark (1963) noted that it was first collected in the state in 1909 (in Jasper County) and suggested that although at the time of his writing the species was reasonably common in southern and central Missouri, it was still uncommon and local farther north. By now, it undoubtedly is present in every county and continues to spread mainly along roadsides and railroads.