1. Corispermum americanum (Nutt.) Nutt. (American bugseed)

Pl. 357 a–c; Map 1543

Plants nearly glabrous to sparsely stellate-hairy, sometimes also with a few unbranched hairs. Stems 10–60 cm long. Leaves 1–5 cm long, linear or sometimes the smaller ones narrowly lanceolate. Inflorescences mostly slender, linear, the flowers more or less evenly spaced, only slightly overlapping. Bracts 2–10 mm long, ovate to narrowly ovate, those of the median and upper flowers about as wide as the fruits, those of the lowermost flowers conspicuously narrower than the fruits. Fruits 3.5–4.5 mm long, broadly obovate to nearly circular in outline, usually rounded at the tip, the wing relatively well developed (0.3–0.5 mm wide), the body light brown to dark brown or dark olive green. August–October.

Known only from historical collections from Clark and Jackson Counties (western U.S. east to New York, Ohio, and Texas; Canada, Mexico). Disturbed, sandy areas.

Plants from Clark County were labeled as being introduced, but the status of the Jackson County populations was not indicated. Corispermum americanum is a morphologically variable species. Mosyakin (1995) treated some populations from the southwestern United States and adjacent Mexico with slightly larger fruits and somewhat more slender, interrupted spikes as var. rydbergii Mosyakin, but these grade into the typical phase too much to warrant formal taxonomic recognition. Although many of the North American specimens of this species originally were determined as C. hyssopifolium L., Steyermark (1963) treated the few Missouri collections as C. nitidum Kit. ex Schult. In the strict sense, C. nitidum supposedly is restricted to eastern Europe (Mosyakin, 1995), but occasional North American specimens seem virtually indistinguishable from those collected in the Old World, even using the characters provided by Mosyakin.