Comments
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Inglês
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fornecido por eFloras
Xanthisma gracile is a species of the Southwest that has been introduced in Maine and possibly other eastern states.
Xanthisma gracile is treated here in the broad sense, to include the n = 4 Haplopappus ravenii in addition to the n = 2 and 3 chromosomal races. According to R. C. Jackson (1962, 1971), the n = 4 race can be distinguished from the other two races on the basis of floret and phyllary morphology. The former is said to possess fewer and shorter pappus bristles, shorter cypselae, and phyllaries that are covered by stiffer, more erect hairs. I have been unable to make this distinction with confidence. It is true that H. ravenii (based on specimens from its described geographic range, but not confirmed by chromosome counts) has phyllaries with often sparse, ascending to spreading hairs versus more numerous, longer, and generally appressed. Unfortunately, in surveying several hundred sheets of X. gracile in the broad sense, approximately twenty percent showed intermediacy in this character. Formal recognition of the n = 4 race has been questioned by A. Cronquist (1971) and others.
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Description
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Inglês
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fornecido por eFloras
Annuals, 5–45 cm; taproots 2–5+ cm. Stems 1–15+, often branched at base or throughout, moderately stout to stout, not wiry, moderately hairy (hairs antrorsely appressed). Leaves: basal often withering by flowering, blades 20–60 × 10–25 mm, pinnatifid to 2-pinnatifid; cauline evenly spaced, blades obovate to oblanceolate (proximal), oblong to linear (distal 2 / 3 +), 4–10(–20) × 1–3 mm, markedly reduced distally, margins evenly serrate to serrulate, teeth 3–6 per side, each tipped with prominent white bristle 1.5–2.5 mm, faces moderately hairy (hairs antrorsely appressed). Peduncles moderately hairy (hairs fine, antrorsely appressed, straight to wavy); usually ebracteate. Involucres hemispheric, 0.6–0.8 × 0.8–1.3 cm. Phyllaries in 4–5 series, linear to narrowly spatulate, 2–7 mm, apices usually acuminate, sometimes rounded, tipped by white bristle, faces hairy (moderately antrorsely appressed hairs), sparsely and minutely stipitate-glandular distally. Ray florets 12–26; corollas yellow, tubes 2.2–3 mm, laminae 6–9.5 × 1–2.5 mm. Disc florets 50–100+; corollas 4–5 mm. Cypselae narrowly obovoid to oblanceoloid, 1.5–2.8 mm, nerves 24–28, faces sparsely whitish hairy; pappi whitish to tawny, 4–5 mm, bristles progressively longer adaxially. 2n = 4, 6, 8.
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- Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
Synonym
(
Inglês
)
fornecido por eFloras
Dieteria gracilis Nuttall, Proc. Acad. Nat. Sci. Philadelphia 4: 22. 1848; Haplopappus gracilis (Nuttall) A. Gray; H. ravenii R. C. Jackson; Machaeranthera gracilis (Nuttall) Shinners
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- Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA
Xanthisma gracile
(
Inglês
)
fornecido por wikipedia EN
Xanthisma gracile[2] is a species of annual flowering plant in the family Asteraceae known by the common names slender goldenweed[3] and annual bristleweed.[4]
Range and habitat
It is native the southwestern United States and northern Mexico, where it grows in the deserts and plateaus.
Growth pattern
It is a bristly annual herb growing erect up to 45 cm tall.
Leaves and stems
The oval or oblong leaves are 1–3 cm long and divided into lobes or teeth tipped with bristles.
Flowers and fruit
The inflorescence bears one or more flower heads lined with pointed, roughly hairy phyllaries. The head has a center of many yellow disc florets and a fringe of 16 to 18 yellow ray florets roughly a centimeter long. The fruit is a woolly achene 2 to 3 millimeters long tipped with a pappus.
Genetics
Xanthisma gracile has extra chromosomes that do not have any functional genes (B chromosomes), and about which little is known.[4]
References
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Xanthisma gracile: Brief Summary
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Inglês
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fornecido por wikipedia EN
Xanthisma gracile is a species of annual flowering plant in the family Asteraceae known by the common names slender goldenweed and annual bristleweed.
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Xanthisma gracile
(
Vietnamita
)
fornecido por wikipedia VI
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Xanthisma gracile: Brief Summary
(
Vietnamita
)
fornecido por wikipedia VI
Xanthisma gracile là một loài thực vật có hoa trong họ Cúc. Loài này được (Nutt.) D.R.Morgan & R.L.Hartm. mô tả khoa học đầu tiên năm 2003.
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