2. Corispermum americanum (Nuttall) Nuttall, Trans. Amer. Philos. Soc., n.s. 5: 165. 1834.
Corispermum hyssopifolium Linnaeus var. americanum Nuttall, Gen. N. Amer. Pl. 1: 4. 1818; C. imbricatum A. Nelson; C. marginale Rydberg; C. simplicissimum Lunell
Plants branched from or beyond base (rarely simple or with few simple branches), 10-35(-50) cm, sparsely covered with dendroid or stellate hairs, often becoming glabrous. Leaf blades linear or narrowly linear (occasionally linear-lanceolate or almost filiform), usually plane or occasionally folded (especially in dry plants), 1.5-3.5(-4) × 0.1-0.3 cm. Inflorescences usually lax, interrupted, rarely ± condensed distally, linear, narrowly linear, or occasionally narrowly clavate. Bracts ovate-lanceolate,lanceolate, linear-lanceolate, or occasionally proximal ones almost linear, much longer than distal, 0.5-2(-3.5) × (0.2-)0.3-0.7 cm. Perianth segment 1. Fruits yellowish brown, greenish brown, light brown, or brown, often with reddish brown spots and whitish warts, slightly convex abaxially, usually plane or slightly concave adaxially, obovate or obovate-elliptic, usually broadest beyond middle, (2.3-)2.5-4.5 × 2-3.5 mm, shiny or dull; wing translucent, thin, (occasionally translucent only at margin, thick), (0.15-)0.2-0.3(-0.4) mm wide, margins entire or rarely indistinctly erose, apex broadly triangular, less commonly truncate or rounded.
Varieties 2 (2 in the flora): North America, Mexico.
Corispermum americanum var. americanum may also occur in British Columbia, where only immature specimens have been seen. Specimens from Oregon and Wyoming are transitional toward Corispermum villosum. The names C. hyssopifolium and C. nitidum were commonly misapplied to this native species by many authors (see also note under C. nitidum).