Compilation
Machaeranthera boltoniae

Annuals, 25–150 cm. Stems and branches often sparsely appressed-hairy, stipitate-glandular distally, occasionally proximally. Distal leaf blades lanceolate to narrowly elliptic or linear, smallest 2.5–5 × 0.7–1.5 mm, bases cuneate to slightly cordate, sometimes slightly clasping. Involucres hemispheric, 4–5 mm. Phyllaries unequal; outer oblong to narrowly elliptic to lanceolate, 2–2.5 × 0.6–0.9 mm, mostly herbaceous, bases inconspicuously indurate, scarious margins absent or obscured by stipitate glands; inner oblanceolate to lanceolate or linear-lanceolate, 3–5 × 0.7–1 mm, bases indurate, margins scarious. Receptacles flat to convex, 1.8–4 mm wide. Ray florets 20–40; laminae 5–9 × 0.5–1 mm. Disc florets 40–75; corollas 2–3.5 mm. Ray cypselae 1–1.8 mm, sparsely appressed-hairy. Disc cypselae 1.2–2.2 mm, sparsely appressed-hairy; pappi 30–45, 1.5–3 mm. 2n = 8.