1. Aphanostephus skirrhobasis (DC.) Trel. var. skirrhobasis (Arkansas lazydaisy)

Map 960

Plants annual, usually relatively slender, with taproots, the vegetative portions moderately to densely short-hairy (the whole plant often appearing grayish). Stems 1 or few, 5–35(–50) cm long, erect or ascending, unbranched or with few to several loosely to strongly ascending branches from near the base or above the midpoint. Basal leaves sometimes withered by flowering time, 2–7 cm long, 1–2 cm wide, the blade oblanceolate to broadly oblanceolate, rounded to bluntly pointed at the tip, long-tapered to the sometimes short-petiolate base, the margins finely to relatively coarsely scalloped or bluntly toothed from just below the broadest portion to the tip (occasionally appearing lobed). Stem leaves often somewhat reduced toward the tip, 1–5 cm long, rounded to bluntly or sharply pointed at the tip, more or less tapered to a usually sessile, nonclasping base, the margins entire or few-toothed toward the tip. Inflorescences of solitary or rarely paired heads at the branch tips, these relatively long, bractless or nearly so. Heads radiate, not sticky or resinous. Involucre 5–8 mm long, cup-shaped to shallowly cup-shaped. Involucral bracts in 4 or 5 unequal, overlapping series, narrowly lanceolate to narrowly oblong-lanceolate, the tip ascending, with a slender, green or brown central stripe and broad, thin, pale margins. Receptacle conical, with minute, irregular ridges around the concave attachment points of the florets. Ray florets 18–45, pistillate, the corolla 8–15 mm long, white, often with a longitudinal pinkish or purplish central line or band on the undersurface, withered but persistent at fruiting, the base becoming pale, somewhat hardened, swollen, and fused to the tip of the maturing fruit. Disc florets numerous (usually more than 250), perfect, the corolla 2.0–2.5 mm long, yellow (often with faint orange lines or mottling), persistent at fruiting, the base becoming pale, somewhat hardened, swollen, and fused to the tip of the maturing fruit. Pappus of the ray and disc florets similar or absent in the ray florets, when present a low, irregular crown (often appearing somewhat toothed), 0.1–0.3 mm long, white or light tan. Fruits 1.5–2.2 mm long, more or less cylindrical but expanded apically into the persistent corolla base and often somewhat 4-angled in cross-section, the surface with 4–12 rounded ribs (appearing finely 4–12-grooved), sparsely and minutely hairy, the hairs hooked or coiled at the tip, yellowish white to tan. 2n=6. May–August.

Introduced, known thus far from a single collection from St. Louis (native of New Mexico to Louisiana north to Kansas and Arkansas; introduced in Missouri). Railroads.

This species was collected in 1961 by Viktor Mühlenbach during his botanical surveys of the St. Louis railyards, but originally it was misidentified as an Astranthium. The specimen was redetermined in 2002 by Guy Nesom of the Botanical Research Institute of Texas.

Turner (1984) treated A. skirrhobasis as consisting of three varieties. The var. thalassius Shinners is a low, bushy plant with thickened leaves that grows on sand dunes in the Gulf Coastal Plain of the southeastern U.S. and adjacent Mexico. The var. kidderi (S.F. Blake) B.L. Turner, which occurs in Texas and adjacent Mexico, is superficially similar to var. skirrhobasis but differs in its pappus of 5 or 10 well-developed scales.