Chrysothamnus humilis |
Chrysothamnus |
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Truckee green rabbitbrush, Truckee rabbitbrush |
rabbit-brush |
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Habit | Shrubs, 10–30 cm; with woody, branched caudices, bark becoming dark gray, fibrous with age. | Shrubs or subshrubs, 8–120 cm (often rounded, compact; usually with woody, often highly branched caudices). | ||||||||||||||||||||||||||||||||
Stems | ascending, green, sparsely to densely puberulent, sparsely glandular. |
ascending to erect or spreading (greenish when young, with age, bark tan to gray, flaky or fibrous), simple (branched in arrays, sometimes ridged from leaf bases), glabrous, hairy, or stipitate-glandular, sometimes gland-dotted, often resinous. |
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Leaves | ascending to spreading; sessile; blades with faint midnerves and pair of collaterals, narrowly elliptic to oblanceolate, 10–30 × 0.7–1.2 mm, flat to sulcate, apices acute (often apiculate), faces moderately puberulent, sparsely stipitate-glandular. |
cauline (ascending or spreading, sometimes deflexed, falcate or recurved); alternate; short-petiolate or sessile; blades with usually evident midnerves plus 0–2 pairs of fainter collateral nerves (secondary nerves raised and reticulate in C. eremobius), filiform, lanceolate, elliptic, or obovate (flat or sulcate, sometimes twisted or folded), margins entire, sometimes hirtellous to ciliate (apices usually acute, sometimes apiculate or spinulose), faces glabrous or hairy, sometimes gland-dotted, often resinous. |
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Involucres | turbinate, 6–10 × 3–4 mm. |
usually turbinate, obconic, or cylindric, sometimes hemispheric, (5–15 ×) 1.5–15 mm. |
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Receptacles | convex, pitted, epaleate. |
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Ray florets | 0. |
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Disc florets | 2–3(–4); corollas 5.5–8 mm, lobes 1–1.7 mm; style branches 2–2.7(–3.4) mm (included in or barely surpassing spreading corolla lobes), appendages 0.8–1.4 mm (lengths about equaling stigmatic portion). |
2–40+ (often 5–6); corollas yellow, tubes shorter than campanulate to funnelform throats, lobes 5, erect to spreading, triangular to lanceolate; style-branch appendages mostly attenuate. |
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Phyllaries | (12–)14–18 in 3–4 series, ± in vertical ranks, mostly tan, sometimes green-tipped, ovate or oblong to elliptic, unequal, 2.5–7.5 × 1–1.8 mm, chartaceous, outer ± herbaceous wholly or distally, weakly keeled, midveins faint, apices acute to obtuse, faces sparsely puberulent. |
12–60+ in (2–)3–7 series (in vertical ranks or spirals, tan, sometimes green and/or purplish subapically or along midveins), usually evidently 1-nerved (often keeled, sometimes flat to convex), linear to elliptic, lanceolate to ovate, or obovate to spatulate, unequal, chartaceous, outer sometimes herbaceous, margins scarious (entire, ciliolate to erose, apices acute to acuminate or rounded, sometimes apiculate to cuspidate or cupped), faces glabrous or hairy, often resinous. |
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Heads | in densely cymiform arrays, often overtopped by distal leaves. |
discoid (usually short-pedunculate), borne singly or in condensed cymiform clusters, these in usually paniculiform, corymbiform, rarely racemiform arrays. |
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Cypselae | reddish brown, turbinate, 4–6 mm, densely hairy; pappi tan, 5–7 mm. |
(tan to reddish brown) turbinate to elliptic or cylindric, sometimes ± flattened to 4–5-angled, often 5–10-ribbed, faces glabrous or densely hairy, sometimes glandular; pappi persistent, of 15–50+, tan, stramineous, or white, fine to coarse, barbellate, apically attenuate bristles in 1 series (of 12–15, white to stramineous, lanceolate or lance-linear scales in C. stylosus). |
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x | = 9. |
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2n | = 18. |
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Chrysothamnus humilis |
Chrysothamnus |
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Phenology | Flowering summer–fall. | |||||||||||||||||||||||||||||||||
Habitat | Sagebrush grasslands, open slopes in deserts, tolerant of alkali | |||||||||||||||||||||||||||||||||
Elevation | 1400–3100 m (4600–10200 ft) | |||||||||||||||||||||||||||||||||
Distribution |
CA; ID; NV; OR; WA
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w North America |
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Discussion | Species 9 (9 in the flora). Phylogenetic and systematic studies have shown that traditional Chrysothamnus should be re-circumscribed (G. L. Nesom and G. I. Baird 1993; R. P. Roberts 2002; Roberts and L. E. Urbatsch 2003, 2004). Species formerly in the genus have been placed in Cuniculotinus, Ericameria, and Lorandersonia (Roberts and Urbatsch 2004; Roberts et al. 2005; Urbatsch et al. 2005). Additional modifications to Chrysothamnus have been the inclusion of Hesperodoria scopulorum and of the monospecific Vanclevea (Roberts and Urbatsch 2004). The present treatment is based partly on that by L. C. Anderson (1986). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 20, p. 189. | FNA vol. 20, p. 187. | ||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Astereae > Chrysothamnus | Asteraceae > tribe Astereae | ||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||
Subordinate taxa | ||||||||||||||||||||||||||||||||||
Synonyms | C. viscidiflorus subsp. humilis | Vanclevea | ||||||||||||||||||||||||||||||||
Name authority | Greene: Pittonia 3: 24. (1896) | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 323. (1840) | ||||||||||||||||||||||||||||||||
Web links |