Rudbeckia hirta L. (var. pulcherrima Farw., if accepted), brown–eyed susan, black–eyed susan. Annual in range (short–lived perennial herb), taprooted, not rosetted, 1–stemmed at base, often unbranched or later robust plant with ascending flowering branches above midplant from successive nodes, erect to ascending, in range 25—60 cm tall; shoots with only cauline leaves, conspicuously hispid–hirsute having hairs swollen at base mostly 1—2 mm long and conspicuously swollen at cell boundaries, aging scabrous with persistent hair bases.
Stems initially ridged aging cylindric, in range to 6 mm diameter, with 3 ridges descending from each leaf, tough, internode < leaf.
Leaves helically alternate, simple, petiolate to sessile (the uppermost cauline leaves) but never clasping, without stipules; petiole indistinct from blade, 0—several mm long; blade ovate or elliptic to obovate (lower cauline leaves), 10—55 × 3.5—24 mm, tapered to long–tapered at base, entire to remotely short–toothed on margins, acute (obtuse) at tip, pinnately veined with 1 vein at base with 1—2 principal lateral veins several mm from base raised on lower surface.
Inflorescence head, solitary and terminal on a long peduncle, head radiate, in range 19—60 mm across, with 8—12 neuter ray flowers and 200+ bisexual disc flowers, the disc flowers in range on a conelike mound 4—11 × 7—17 mm (length < width) somewhat truncate with depressed center while flowering, the mound purple with some brown and covered with appressed, stiff short hairs, bracteate, hispid–hirsute; bract subtending peduncle leaflike and short–petiolate to sessile, petiole flattish on upper surface, to 1 mm long, whitish, blade elliptic, 10—25 × 3.2—10 mm, with midrib strongly raised on lower surface; peduncle 5–ridged or 8–ridged, 48—125 × 1.5 mm (ca. 1/3 plant height), stiff–hairy along ridges, lacking bracts along peduncle; involucre dishlike with widely spreading to somewhat deflexed phyllaries, ca. 14—30 mm across, phyllaries 13—18 (green) in 3—4 series, phyllaries 8 or 13 in outer series lanceolate to oblong, in range 13—16 × 2—2.4 mm, hispid–hirsute, upper surface somewhat cobblestonelike, inner series mostly of 5 phyllaries with an ovate lower portion 3—3.5 mm long and narrowly triangular upper portion to 7 mm long decreasing upward, upper surface of lower portion strigose with upward–pointing hairs and of upper portion glabrous with stiff–ciliate margins; often the two innermost phyllaries subtending ray flowers resembling bractlets (paleae); receptacle narrowly conic, ca. 5 × 1 mm, densely covered by helically alternate bractlets (paleae), palea subtending each disc flower (+ several ray flowers), acute–obovate slightly keeled to keeled, in range 4—5 × 1.5—1.8 mm, white at base to above midpoint and pale purple then purple approaching tip with 3 purple veins from base (central vein later), stiff–ciliate on margins approaching tip with the longest hair terminal, upper (inner) surface glabrous, outer (lower) surface short–hirsute except at base.
Ray flower bilateral, 3—8 mm across; calyx (pappus) absent; corolla unlobed sometimes with 1—2 short teeth; tube flattened front–to–back, < 0.5 mm long; limb elliptic to oblong, in range < 9—19 × 3—8 mm, dark yellow with deep red blotch at base appearing purple to brownish, the blotch flaring and irregularly lobed to jagged, 2—4 mm long, obtuse to short–notched at tip, upper surface glabrous and minutely papillate, lower surface short–strigose to short–hirsute with upward–pointing hairs and some sessile spheric glandular hairs; stamens absent; pistil 1, sterile; ovary inferior, narrowly top–shaped flattened front–to–back, ca. 2.5 × 1 mm, white and purplish brown, faces glabrous, with stiff short–hairs to 0.25 mm long along top rim; style absent.
Disc flower bisexual, radial, < 1 mm across; calyx (pappus) absent; corolla 5–lobed, ca. 3 mm long; tube somewhat squarish, 0.7—0.8 mm long, white; throat angled, 0.6—0.65 mm diameter, lower portion white with purple stripes, upper portion purple; lobes widely spreading aging somewhat reflexed, triangular, 0.7 × 0.5 mm, purple to brown; stamens 5, attached to top of corolla tube; filaments 0.5 mm long, white; anthers fused into cylinder surrounding style, basifixed, dithecal, ca. 1.6 mm long including appendage at tip, deep purple, the appendages exserted, triangular, 0.4 mm long; pollen orange–yellow; pistil 1; ovary inferior, narrowly inverted pyramidal and mostly 4–sided, 1 × 0.4 mm, white, 1–chambered with 1 ovule; nectary disc surrounding base of style at top of ovary, 0.25 × 0.30.35 mm; style slender, 1.8 mm long, white at base to deep purple above, 2–branched from below midpoint, the stigmatic branches exserted < 1 mm above anther appendages and appressed, conspicuously short–hairy.
Fruits cypselae (disc flowers only) obelisklike and 4–sided, ± 2 × 0.4—0.45 mm, black, finely textured with cells in well–defined vertical files; pappus absent.
A. C. Gibson