Xylorhiza glabriuscula |
Xylorhiza |
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common woody aster, smooth woody-aster |
desert-aster, woody-aster |
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Habit | Subshrubs, 10–25 cm. | Perennials, subshrubs, or shrubs, 10–80(–150) cm (taproots woody, branched, caudices persistent). | ||||||||||||||||||||||||||||||||
Stems | branched mostly in proximal 3/4 (leafy 2/3+ their lengths), villoso-puberulent or glabrous, eglandular. |
(often white-barked) erect, branched, glabrous or villous to tomentose, sometimes stipitate-glandular. |
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Leaves | blades oblanceolate, 2.5–8 mm wide, bases attenuate, not clasping, margins flat, entire, faces villoso-puberulent or glabrous, eglandular. |
cauline; alternate; sessile or subpetiolate; blades mostly 1-nerved, linear to lanceolate or oblanceolate, oblong, or narrowly elliptic, margins entire or dentate-spinulose (apices acute), faces glabrous or sparsely tomentose to villous, sometimes stipitate-glandular. |
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Peduncles | 2–6 cm. |
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Involucres | 7–14 × 12–25 mm. |
campanulate to hemispheric, 7–20 × 12–40(–48) mm. |
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Receptacles | flat, pitted, epaleate. |
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Style | -branch appendages equal or shorter than stigmatic lines. |
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Ray florets | 12–25; corollas white. |
(4–)12–60(–85), pistillate, fertile; corollas white to light blue or purple (coiling at maturity). |
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Disc florets | 30–140, bisexual, fertile; corollas yellowish, tubes slightly shorter to longer than narrowly funnelform throats, lobes 5, spreading, triangular; style-branch appendages lanceolate. |
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Phyllaries | 25–45 in 3–6 series, 1-nerved (keeled), narrowly lanceolate, unequal, proximally white-indurate, margins scarious (apices green, erect or spreading), abaxial faces glabrous or sparsely tomentose to villous, sometimes stipitate-glandular. |
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Heads | radiate, borne singly (terminal on ebracteate peduncles). |
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Cypselae | (brownish) fusiform to linear or ovoid, ± compressed to subterete, 4-ribbed, faces sericeous (hairs subappressed, long, silky); pappi persistent, of 30–45 tawny, stout, unequal, often flattened, barbellate, apically attenuate bristles in 2–3 series. |
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x | = 6. |
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2n | = 12. |
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Xylorhiza glabriuscula |
Xylorhiza |
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Phenology | Flowering May–Jun(–Jul). | |||||||||||||||||||||||||||||||||
Habitat | Open sites, selenious, alkaline clays, dominated by sagebrush, saltbush, greasewood, and grasses | |||||||||||||||||||||||||||||||||
Elevation | 1100–2300 m [3600–7500 ft] | |||||||||||||||||||||||||||||||||
Distribution |
CO; MT; SD; UT; WY
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sw United States; nw Mexico |
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Discussion | Species 10 (9 in the flora). Xylorhiza species were considered by A. Cronquist and D. D. Keck (1957) to be primitive members of the genus Machaeranthera, where they were recently maintained (Cronquist 1994). T. J. Watson (1977) and other contemporary botanists, however, have recognized Xylorhiza as a distinct genus characterized by the following features: perennial herbs, subshrubs, and shrubs from large, woody taproots with woody, branched, persistent caudices; large, single heads; long phyllaries with erect or spreading apices; white or bluish rays; large cypselae; and vernal flowering. The base chromosome number of Xylorhiza (x = 6) also contrasts with that of Machaeranthera (x = 4 or 5). Two sections were recognized by Watson: sect. Xylorhiza (subshrubs or perennial herbs) and sect. Californica T. J. Watson (shrubs, including X. cognata, X. orcuttii, and the Mexican endemic X. frutescens). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 20, p. 407. | FNA vol. 20, p. 406. | ||||||||||||||||||||||||||||||||
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Synonyms | Aster parryi, Machaeranthera glabriuscula, Machaeranthera glabriuscula var. villosa, X. glabriuscula var. villosa, X. villosa | Machaeranthera section X. | ||||||||||||||||||||||||||||||||
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 297. (1840) | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 297. (1840) | ||||||||||||||||||||||||||||||||
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