Flora of North America species comparison

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Chaenactis thompsonii

Chaenactis sect. Macrocarphus
Chaenactis thompsonii

Thompson's pincushion
Habit Perennials, 10–30 cm (not or scarcely cespitose, not matted); proximal indument thinning with age, grayish, arachnoid-sericeous to thinly lanuginose. Biennials, perennials, or subshrubs (rarely flowering first year); proximal indument predominantly arachnoid, lanuginose, or pannose (rarely glabrescent), not farinose.
Stems

mostly 5–15+, ascending to erect.

1–25+, prostrate to erect;

branches mainly proximal.
Leaves

mostly cauline, 2–5 cm;

largest blades ± elliptic, ± plane, 1-pinnately lobed;

lobes mostly 2–5 pairs, remote, ± plane.

largest blades deltate, elliptic, linear, or ovate, (0–)1–2-pinnately or -subpalmately lobed, gland-dotted beneath indument.
Peduncles

ascending to erect, 2–5 cm.

prostrate to erect.
Involucres

± obconic.

Corollas

7–9 mm.

white to pinkish or cream, actinomorphic, ± equal.
Phyllaries

longest (10–)12–15 mm;

outer closely lanuginose, not stipitate-glandular, apices erect, ± rigid.

outer ± blunt.
Heads

mostly 1–3 per stem.

discoid.
Cypselae

7–9 mm (eglandular);

pappi: longest scales 3.5–5 mm.

± terete;

pappi of (8–)10–20 scales in 2–4 equal or gradually unequal series.
x

= 6.

Chaenactis thompsonii

Chaenactis sect. Macrocarphus
Phenology Flowering Jun–Aug.
Habitat Rocky or gravelly serpentine slopes, scree, talus, openings in or above conifer forests
Elevation (900–)1200–2200 m ((3000–)3900–7200 ft)
Distribution
from FNA
WA
[WildflowerSearch map]
[BONAP county map]
w North America; nw Mexico
Discussion

Of conservation concern.

Chaenactis thompsonii appears to be sister to C. evermannii; it is known from the mountains of central and northwestern Washington. The similar habits of C. thompsonii and C. ramosa (= C. douglasii var. douglasii) appear to result from convergent evolution in the distinctive habitat of their type localities (Wenatchee Mountains), not from a close genetic relationship as suggested by Cronquist.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
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)
C. parishii
3. Phyllaries: longest 14–18 mm, outer predominantly stipitate-glandular (other indument none or sparse)
C. 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
C. douglasii
4. Outer phyllaries closely lanuginose, not stipitate-glandular; largest leaf blades ± plane, 1-pinnately lobed, lobes remote, ± plane (Washington)
C. 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)
C. 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
C. 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
C. 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
C. 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
C. suffrutescens
10. Largest leaf blades ± elliptic to slightly ovate, primary lobes (4–)5–9(–12) pairs, ± congested, scarcely imbricate; not s California
C. douglasii
10. Largest leaf blades linear-cylindric to ± fusiform, primary lobes (7–)10–18+ pairs, ± imbricate; s California
C. santolinoides
Source FNA vol. 21, p. 407. FNA vol. 21, p. 403.
Parent taxa Asteraceae > tribe Heliantheae > subtribe Chaenactidinae > Chaenactis > sect. Macrocarphus Asteraceae > tribe Heliantheae > subtribe Chaenactidinae > Chaenactis
Sibling taxa
C. alpigena, C. artemisiifolia, C. carphoclinia, C. cusickii, C. douglasii, C. evermannii, C. fremontii, C. glabriuscula, C. macrantha, C. nevadensis, C. nevii, C. parishii, C. santolinoides, C. stevioides, C. suffrutescens, C. xantiana
Subordinate taxa
C. alpigena, C. douglasii, C. evermannii, C. nevadensis, C. parishii, C. santolinoides, C. suffrutescens, C. thompsonii
Synonyms section Macrocarphus
Name authority Cronquist: in C. L. Hitchcock et al., Vasc. Pl. Pacif. N.W. 5: 123, fig. [p. 125]. (1955) (Nuttall) Torrey & A. Gray: Fl. N. Amer. 2: 371. (1842)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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