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Electronic Flora of South Australia genus Fact Sheet

Family: Compositae
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:  500-600 species, almost cosmopolitan.

Biology: No text

Key to Species:
1. Appendages of intermediate bracts with one long spine, often with smaller spinules at the base
 
2. Flowers purple; pappus absent
C. calcitrapa 2.
2. Flowers yellow; pappus of bristles
 
3. Involucre 15-20 mm long; achene c. 4 mm long
C eriophora 4.
3. Involucre 9-12 mm long; achene c. 2.5 mm long
 
4. Spines of involucral bracts 6-9 mm long, with pinnately arranged spinules along the lower portion
C. melitensis 5.
4. Spines of involucral bracts 10-20 mm long, with spinules at the base only
C. solstitialis 9.
1. Appendages of intermediate bracts pectinate or with a number of small subequal spinules
 
5. Appendages pectinate, dark-brown
 
6. Plant tomentose; cauline leaves mostly pinnatipartite
C. cineraria 3.
6. Plant scabrous, pubescent, sometimes slightly cobwebby; cauline leaves entire to remotely dentate
 
7. Appendages 2-3 mm long, obscuring the remainder of the involucre; pappus c. 1 mm long
C. nigra 6.
7. Appendages 1-1.5 mm long, exposing most of the involucre; pappus microscopic
C. nigrescens 7.
5. Appendages entire or with 2-5 spinules, pale-brown
 
8. Involucre 10-20 mm diam.; achenes c. 4 mm long
C. aspera 1.
8. Involucre 5-9 mm diam.; achenes c. 2.5 mm long
C. paniculata 8.

Author: Not yet available


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