Chaenactis sect. Macrocarphus

(Nuttall) Torrey & A. Gray

Fl. N. Amer. 2: 371. 1842.

Basionym: Undefined sect. Macrocarphus Nuttall Trans. Amer. Philos. Soc., n. s. 7: 376. 1841
Treatment appears in FNA Volume 21. Treatment on page 403. Mentioned on page 401, 410.

Biennials, perennials, or subshrubs (rarely flowering first year); proximal indument predominantly arachnoid, lanuginose, or pannose (rarely glabrescent), not farinose. Stems 1–25+, prostrate to erect; branches mainly proximal. Leaves: largest blades deltate, elliptic, linear, or ovate, (0–)1–2-pinnately or -subpalmately lobed, gland-dotted beneath indument. Heads discoid. Peduncles prostrate to erect. Phyllaries: outer ± blunt. Corollas white to pinkish or cream, actinomorphic, ± equal. Cypselae ± terete; pappi of (8–)10–20 scales in 2–4 equal or gradually unequal series. x = 6.


w North America, nw Mexico.


Species 8 (8 in the flora).

Species of sect. Macrocarphus occur mainly in montane to alpine habitats; all except Chaenactis douglasii are narrowly distributed. With C. douglasii here broadly defined, all the species of sect. Macrocarphus are sharply distinct.

Selected References



1 Leaves ± cauline and, often, basal; plants not or scarcely cespitose, not matted; heads (1–)2–25+ per stem > 2
1 Leaves ± basal; plants cespitose or ± matted; heads 1(–3) per stem > 5
2 Subshrubs (usually); proximal indument (especially stems) persistent, whitish, densely lanuginose or pannose; largest leaf blades deltate to ovate, ± plane (California) > 3
2 Biennials or perennials (rarely slightly woody or flowering first year); proximal indument ± thinning with age, grayish, arachnoid to ± lanuginose; largest leaf blades ± elliptic or lanceolate to ovate, plane or ± 3-dimensional > 4
3 Phyllaries: longest 10–13 mm, outer predominantly arachnoid to closely lanuginose (sparsely, if at all, stipitate-glandular) Chaenactis parishii
3 Phyllaries: longest 14–18 mm, outer predominantly stipitate-glandular (other indument none or sparse) Chaenactis suffrutescens
4 Outer phyllaries usually densely, sometimes sparsely or obscurely, stipitate-glandular and, often, arachnoid, lanuginose, and/or villous; largest leaf blades ± 3-dimensional, usually 2-pinnately lobed, primary lobes ± congested, ultimate lobes ± involute and/or twisted Chaenactis douglasii
4 Outer phyllaries closely lanuginose, not stipitate-glandular; largest leaf blades ± plane, 1-pinnately lobed, lobes remote, ± plane (Washington) Chaenactis thompsonii
5 Outer phyllaries predominantly arachnoid, sericeous, or ± lanuginose (sparsely, if at all, stipitate-glandular) > 6
5 Outer phyllaries predominantly or evidently stipitate-glandular (other indument none, sparse, or ± arachnoid) > 8
6 Cypselae sparsely glandular amidst other indument; largest leaf blades 2-pinnately lobed (± 3-dimensional, primary lobes 4–12 pairs, peduncles mostly ascending to erect) Chaenactis douglasii
6 Cypselae eglandular; largest leaf blades (0–)1(–2)-pinnately or -subpalmately lobed (± plane, and/or primary lobes 0–4 pairs, and/or peduncles mostly prostrate) > 7
7 Longest pappus scales 2.5–4.5 mm (lengths 0.4–0.8 times corollas); leaf blades ± plane; peduncles mostly ascending to erect; Idaho Chaenactis evermannii
7 Longest pappus scales 5–8 mm (lengths 0.9–1 times corollas); leaf blades ± plane or 3-dimensional; peduncles mostly prostrate; California, Nevada Chaenactis alpigena
8 Largest leaf blades deltate to ovate, ± plane, ultimate lobes ± plane > 9
8 Largest leaf blades linear-cylindric to ± elliptic or slightly ovate, ± 3-dimensional, ultimate lobes ± involute and/or twisted > 10
9 Plants 2–10(–12) cm; leaves 2.5–5 cm; longest phyllaries 9–12(–14) mm; corol-las 5.5–8 mm; longest pappus scales 3–5 mm Chaenactis nevadensis
9 Plants (10–)25–45(–60) cm; leaves 5–10 cm; longest phyllaries 14–18 mm; corollas 8.5–10 mm; longest pappus scales 7–9 mm Chaenactis suffrutescens
10 Largest leaf blades ± elliptic to slightly ovate, primary lobes (4–)5–9(–12) pairs, ± congested, scarcely imbricate; not s California Chaenactis douglasii
10 Largest leaf blades linear-cylindric to ± fusiform, primary lobes (7–)10–18+ pairs, ± imbricate; s California Chaenactis santolinoides
James D. Morefield +
(Nuttall) Torrey & A. Gray +
Undefined sect. Macrocarphus +
w North America +  and nw Mexico. +
Fl. N. Amer. +
Undefined (tribe Undefined) subtribe Bahiinae +  and Undefined (tribe Undefined) subtribe Palafoxiinae +
Chaenactis sect. Macrocarphus +
Chaenactis +
section +