Flora of North America species comparison

erect (branched from bases).

mostly opposite;

blades not lobed, linear to acerose, 10–18 mm.

mostly cauline, sometimes basal or basal and cauline; mostly opposite (distal sometimes alternate) or mostly alternate; petiolate or sessile;

blades usually elliptic, filiform, lanceolate, linear, or ovate, often 1(–2)-pinnately lobed, ultimate margins entire or toothed (often proximally bristly-ciliate), faces glabrous or puberulent to tomentose (usually bearing oil-glands, embedded pellucid glands filled with strong-scented, essential oils).

0–10 mm, puberulent or glabrous.

campanulate to cylindric, 5–7 mm.

campanulate, cylindric, hemispheric, obconic, or turbinate.

flat or convex to hemispheric or conic, epaleate (receptacles sometimes pitted, pit margins sometimes fimbrillate to laciniate).

7–8;

corollas lemon-yellow, laminae 5–6 × 2–3 mm.

0 or 1–21+, pistillate, fertile;

corollas yellow to orange (sometimes with brown or mostly brown) or white to pink, magenta, or reddish purple.

18–25+;

corollas pale yellow, 3–4 mm.

1–120+, usually bisexual and fertile [functionally staminate];

corollas yellow to orange or brown, or pinkish to purplish or reddish, tubes much shorter than to much longer than cylindric to funnelform throats, lobes 5, deltate to lance-linear (equal or unequal);

anther thecae pale or ± darkened;

stigmatic papillae in 2 lines.

ca. 13, margins of outer distinct less than 1/6 their lengths, abaxial faces puberulent or glabrous.

falling or persistent, 3–21+ in 1–2 series (distinct or ± connate, mostly linear to lanceolate, usually subequal, usually some or all bearing pellucid oil-glands as in leaves).

of 5 lance-linear bractlets, lengths 1/2+ phyllaries.

0 or of 1–22 bractlets.

radiate or discoid (sometimes radiant, e.g., in Thymophylla), usually borne singly, sometimes in loose to crowded, corymbiform or cymiform arrays.

3–3.5 mm;

pappi of ca. 20 scales (each a fascicle of 3–5 bristles), 3–4 mm.

mostly clavate to obpyramidal (lengths usually 2–3+ times diams.), glabrous or hairy;

pappi usually persistent, of 20–50 bristles in 1–2+ series, or of 5–20 (sometimes aristate) scales in 1–2 series, or combinations of bristles and scales in 1–2+ series, rarely coroniform or 0.

= 16, 24.