1. Helminthotheca echioides (L.) Holub (bristly ox-tongue)

Picris echioides L.

Pl. 260 j, k; Map 1066

Plants annual or biennial, usually taprooted. Latex white. Stems solitary or few, 20–80 cm long, erect or ascending, few- to several-branched, finely longitudinally ridged, moderately to densely pubescent with white, spreading hairs, these often somewhat flattened and expanded or swollen at the base, all or most of these barbed at the tip with 2–5 minute, spreading to recurved branches from a knoblike tip. Leaves basal and alternate, not grasslike, the basal leaves often present at flowering and tapered to a sessile or short- to less commonly long-petiolate base, the stem leaves sessile. Leaf blades 2–25 cm long, oblanceolate to elliptic, lanceolate, or narrowly oblong-lanceolate, mostly with rounded basal lobes somewhat clasping the stem, unlobed, the margins entire or with shallow, spreading, broadly triangular teeth and rounded sinuses, both surfaces moderately to densely pubescent with white, spreading hairs, all or most of these barbed at the tip with 2–5 minute, spreading to recurved branches from a knoblike tip, the margins and surfaces also with sparse to moderately dense, short, white to cream-colored prickles. Venation of 1 main vein and sometimes very faint, arching secondary veins. Inflorescences appearing paniculate, the heads mostly in small clusters at the tips of leafy branches, occasionally solitary at the branch tips. Involucre 10–20 mm long at flowering, not or only slightly elongating at fruiting, cup-shaped to broadly urn-shaped, the bracts in 2 series, moderately to densely pubescent with white, spreading hairs (those of the inner series glabrous on the inner surface), all or most of these barbed at the tip with 2–5 minute, spreading to recurved branches from a knoblike tip, the margins, tip, and often midvein also with sparse to moderately dense, short, white to cream-colored prickles; those of the inner series 7–13, lanceolate to narrowly lanceolate, thinner and somewhat papery, ascending at flowering, those of the outer series 3–5, slightly shorter than to slightly longer than those of the inner series, ovate to broadly ovate, thick and leathery, green, loosely ascending at flowering. Receptacle naked, shallowly pitted at the base of each floret. Ligulate florets 30–80. Corollas 10–17 mm long, bright yellow to deep yellow, often somewhat reddish-tinged on the outer surface. Pappus of numerous plumose bristles, white to pale straw-colored, 4–7 mm long, often somewhat shorter on the marginal florets than on the central florets. Fruits 4–8 mm long (including the beak), the body 2.0–2.7 mm long, narrowly oblong-elliptic in outline, somewhat flattened (oval in cross-section), tapered abruptly to a slender beak 1–2 times as long as the body, the pappus attached to an expanded, disclike tip, the body with 5–8 faint, longitudinal nerves and a network of fine, raised cross-wrinkles, otherwise glabrous or the marginal fruits inconspicuously hairy, orangish brown to yellowish brown. 2n=10. July–September.

Introduced, known thus far only from St. Louis (native of Europe, Africa; introduced widely in temperate and tropical regions, including sporadically in the western, midwestern, and northeastern U.S., Canada). Railroads.

This species was first reported for Missouri by Mühlenbach (1979) based on his botanical surveys of the St. Louis railyards.