Family: Asteraceae
Centaurea
Citation:
L., Sp. Pl. 909 (1753).
Derivation: From centaureum majus, the term used by Pliny for a species of this genus associated as a medicinal herb with the centaur Chiron, legendary founder of medicine.
Synonymy: Not Applicable Common name: Knapweeds.
Description:
Annual, biennial and perennial herbs; stems erect or ascending, terete or winged; leaves basal and cauline, alternate, entire to pinnatisect.
Capitula solitary or in groups of 2 or 3, terminal on branches, sessile or pedunculate, ovoid, heterogamous; involucres campanulate to ovoid; bracts herbaceous, with a scarious or hard, pectinate or spiny appendage (obsolete in the innermost bracts), imbricate in several unequal series; receptacle hairy; florets all tubular, the outer ones sterile, often spreading, the inner ones bisexual, fertile; corolla narrow below, funnel-shaped and 5-8-lobed above; anthers shortly tailed at the base, with acute sterile appendages at the apex; style branches diverging at the apex only, obtuse, without sterile appendages.
Achenes oblong, compressed, asymmetric with the hilum at one side; pappus 2-many-seriate, of scales or bristles, or absent.
Distribution:
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500-600 species, almost cosmopolitan.
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Biology:
No text
Key to Species:
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1. Appendages of intermediate bracts with one long spine, often with smaller spinules at the base |
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2. Flowers purple; pappus absent |
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C. calcitrapa 2. |
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2. Flowers yellow; pappus of bristles |
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3. Involucre 15-20 mm long; achene c. 4 mm long |
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C eriophora 4. |
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3. Involucre 9-12 mm long; achene c. 2.5 mm long |
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4. Spines of involucral bracts 6-9 mm long, with pinnately arranged spinules along the lower portion |
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C. melitensis 5. |
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4. Spines of involucral bracts 10-20 mm long, with spinules at the base only |
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C. solstitialis 9. |
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1. Appendages of intermediate bracts pectinate or with a number of small subequal spinules |
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5. Appendages pectinate, dark-brown |
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6. Plant tomentose; cauline leaves mostly pinnatipartite |
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C. cineraria 3. |
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6. Plant scabrous, pubescent, sometimes slightly cobwebby; cauline leaves entire to remotely dentate |
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7. Appendages 2-3 mm long, obscuring the remainder of the involucre; pappus c. 1 mm long |
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C. nigra 6. |
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7. Appendages 1-1.5 mm long, exposing most of the involucre; pappus microscopic |
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C. nigrescens 7. |
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5. Appendages entire or with 2-5 spinules, pale-brown |
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8. Involucre 10-20 mm diam.; achenes c. 4 mm long |
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C. aspera 1. |
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8. Involucre 5-9 mm diam.; achenes c. 2.5 mm long |
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C. paniculata 8. |
Author:
Not yet available
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