Aphanostephus skirrhobasis (DC.) Treal. var. skirrhobasis, arkansas lazydaisy. Annual, taprooted, not rosetted, 1–stemmed at base, when small unbranched, larger individuals with ascending branches from midplant forming flowering canopy, highly variable in size, in range 5— < 50 cm tall; gynomonoecious; shoots with only cauline leaves, short–hirsute.
Stems 5–ridged, to 3 mm diameter, 3–ridged descending from each leaf, striped green and tan, short–hirsute.
Leaves helically alternate, simple, petiolate (lower leaves) and sessile and clasping (most leaves), without stipules; petiole somewhat flattened, to 5 mm long, 3–veined at base; blade ovate or fiddle–shaped to oblanceolate or obovate, < 10—25 × 3—9 mm, tapered or clasping at base, entire, acute (obtuse) often with callus point at tip, pinnately veined with principal veins slightly raised on lower surface.
Inflorescence head solitary, terminal on peduncle, head radiate, 9—35 mm across highly variable), of 9—32 pistillate ray flowers and 25—100+ bisexual disc flowers with disc to 12 mm across, bracteate; bract subtending peduncle leaflike and sessile, oblong, 8—10 × 1.2—2.4 mm; peduncle 8–ridged, to 40 × < 1.5 mm, tough, green, short–hirsute and with scattered minute hairs (duplex); involucre cup–shaped or broadly cup–shaped to hemispheroid, 2.5—9 mm across but inner phyllaries spreading beneath ray corolla limbs, of (14—)25—49 phyllaries in (2—)3—4 series, short–hirsute on exposed tissue, phyllaries unequal, not keeled, and 1–veined, appressed but on wide head 1—3 inner phyllaries suberect and ascending past ray corolla limbs, of the outermost series acute–lanceolate, from 3.5 × 0.8 mm increasing inward to broadly oblanceolate or oblong and acute to short–acuminate at tip, to 8 × 1.5 mm, short–ciliate on margins, middle and inner phyllaries with green axis or midvein sometimes with purple dots and the innermost phyllaries colorless margins with green to red vein or purplish at least at tip; receptacle convex to domelike, lacking bractlets (paleae), shallowly pitted with ring of minute hairs (duplex) to 0.15 mm long surrounding each ovary, hollow beneath receptacle.
Ray flower bilateral, 1.8—7 mm across; calyx (pappus) crownlike (absent), 0.15—0.3 mm long, margin minutely ciliate and sometimes reddish; corolla without lobes and teeth or minutely 2—3–toothed; tube at anthesis bulbous to spheroid and nearly solid, 0.5—1 × 0.65—0.7 mm, white; limb elliptic to oblong–oblanceolate or lanceolate, 5.5—11 × 1.8—2.5 mm, white or tinged purplish on lower surface and without visible venation; stamens absent; pistil 1; ovary inferior, cylindric strongly ribbed and compressed side–to–side, ca. 1.2 × 0.8 × 0.6 mm, ± green, with some minute hairs (duplex), 1–chambered with 1 ovule; style 1—2 mm long, white, 2–branched with stigmatic branches exserted 0.5—0.6 mm.
Disc flower bisexual, radial, 1 mm across, 2.4—3.3 mm long; calyx (pappus) crownlike (absent), 0.15—0.45 mm long; corolla 5–lobed; tube not distinct from throat and ca. 2 mm long, tube narrowly barrel–shaped, 0.5—0.6 mm long, greenish, later enlarging and bulbous (ovoid) nearly solid and hard, upper portion with short hairs, throat narrowly bell–shaped, colorless appearing light yellow (anthers); lobes ascending to suberect, triangular, 0.4—0.45 mm, light yellow or aging with red tip, upper side minutely papillate; stamens 5, attached to top of corolla tube; filaments 0.25—0.3 mm long, white; anthers fused into cylinder surrounding style, basifixed, dithecal, 0.8—1 mm long including appendages, pale yellow to light yellow, longitudinally dehiscent; pollen pale yellow to light yellow; pistil 1; ovary inferior, wedge–shaped strongly ribbed and angular, (0.35—)0.8 × 0.35—0.4 mm, white with greenish ribs, with scattered hairs (duplex) to 0.15 mm long, 1–chambered with 1 ovule; style included with branches scarcely above anther appendages or touching anthers, 1.1—2 mm long, short 2–branched, below fork orangish, the stigmatic branches 0.3—0.4 mm long, yellowish, stigmatic surface somewhat flattened and bearded.
Fruits cypselae (achenes), of ray flowers wedge–shaped strongly ribbed, ± 1.8 × 1.3 mm, of disc flowers columnar strongly ribbed, ± 1.8 × 0.8 mm, tan; pappus crown short on cypsela with longer portions often missing; conic swelling of corolla tube and throat on top of cypsela, ca. 0.7 mm diameter at base, tannish, hard; involucre phyllaries coiled inward.
A. C. Gibson