Tetraneuris linearifolia (Hooker) Greene var. linearifolia, slenderleaf bitterweed. Annual, taprooted, initially rosetted, 1(—several)–stemmed at base, erect to suberect, initially with 1 principal axis forming lateral branches downward from each axillary bud, with inflorescences in range 8—35 cm tall; gynomonoecious; shoots with to 8 basal leaves and several cauline leaves, rosette miniature on the smallest plants, pubescent, gland–dotted with sunken glandular hairs on young stems and leaves and heads aging pinkish.
Stems low–ridged, to 3 mm diameter, with 3 ridges descending from each leaf but ± densely covered with upward–pointing nonglandular hairs concealing sunken glandular heads. Leaves: helically alternate, simple, petiolate (lower leaves) and subsessile (upper leaves), without stipules; petiole flared at base and above flattened to–to–bottom, to 20 mm long, indistinct from blade, 3–veined, with narrow membranous margins; blade linear, or nearly lanceolate to oblanceolate–linear or spatulate (narrowly elliptic–oblanceolate), 5.3—60 × 0.9—5 mm, long–tapered at base, entire, acute at tip, 3–veined from base with white midrib raised on lower surface, fine nonglandular hairs to 4 mm long.
Inflorescence heads, solitary and terminal on long peduncle of each principal shoot, head radiate, 11—26+ mm across, with 4—13 pistillate ray flowers and 8—125+ bisexual disc flowers, disc 3.8—13.5 mm across, bracteate; peduncle arising at or below midplant, erect, straight and slender, 32—170+ × 1.5 mm, appressed–villous or sericeous to short–strigose with upward–pointing hairs concealing inconspicuous glandular hairs colorless at flowering, lacking bracts (calyculus) at top; involucre broadly funnel–shaped to hemispheroid, 3.5—6 × 3—15 mm, in range phyllaries 8—20 in 2—3 series, outer phyllaries ovate and inner phyllaries oblong to narrowly obovate or elliptic, 2—3.5 × 0.8—1.5 mm, finely 2–veined, green but inner phyllaries with colorless margins, colorless margin sometimes with a shoulder, often with a reddish callus at tip, sericeous on green tissue; receptacle convex to domed, lacking bractlets (paleae), with glandular hairs between ovaries.
Ray flower bilateral, 2.5—6.5 mm across (corolla limb); calyx (pappus) of (4—)5—7 awned, scarious scales (aristate), in more than 1 series, ca. 2.5 mm long, scarious portion obovate, 1.2—1.5 mm long, awnlike portion from ca. midpoint with fine point at tip; corolla 3(—4)–lobed; tube 0.8—1.3 × 0.7 mm, pale green, densely short–hairy; limb narrowly fan–shaped to obovate or elliptic, 5—10.5 × 2.5—6.5 mm, orange–yellow with 4 green–yellow raised veins on lower surface, the 2 central veins 2–forked to lobes, lobes obtuse to rounded (acute), 0.2—2 mm long, lower surface short–hirsute and with conspicuous short–stalked glandular hairs with spheric, colorless heads; stamens absent; pistil 1; ovary inferior, narrowly inversely pyramidal, ± 1.7 × 0.5 mm, greenish, oblique at base, short–hairy with ascending hairs, 1–chambered with 1 ovule; style with tips of stigmatic branches exserted or scarcely so, ca. 1.8 mm long, 2–branched from midpoint.
Disc flower radial, ca. 1 mm across, 4—4.5 mm long; in bud truncate on top with a thick cover of yellow–orange (golden) hairs ± 0.3 mm long, the hairs sometimes with a scarlet terminal cell; calyx (pappus) of (4—)5—7 awned, scarious scales (aristate), in more than 1 series, ca. 2.5 mm long, scarious portion obovate, 1.2—1.5 mm long, awnlike portion from ca. midpoint with fine point at tip; corolla 4—5–lobed, ca. 2 mm long; tube short–cylindric, 0.25—0.3 × 0.35 mm; throat ± bell–shaped, 1.4—1.5 × 0.7 mm, colorless with 8 or 10 yellow–orange ribs = veins to lobes and sinuses, having some short hairs; lobes deltate, ca. 0.35 mm, somewhat hidden by colored hairs on outer surface; stamens 4—5, attached at top of corolla tube; filaments to 0.5 mm long; anthers fused into cylinder surrounding style, basifixed, dithecal, included, 1 mm long, whitish, longitudinally dehiscent; pollen pale yellow; pistil 1; ovary inferior, narrowly inversely pyramidal, ± 1.7 × 0.5 mm, greenish, oblique at base, short–hairy with ascending hairs, 1–chambered with 1 ovule; style included, ca. 1.8 mm long, 2–branched from midpoint.
Fruits cypselae (achenes) monomorphic; club–shaped, ca. 2 × 1 mm, with short ascending hairs; pappus of 5+ aristate scales persistent.
A. C. Gibson