182 SYKGENESIA. NECESSARIA. 



594. CENTALREA. L, (Knapweed, &c.) 



Calix various, liaijs funnelform, irregular. 

 Eeceptacle setose. Pappus simple, often pilose. 



Generally herbaceous; leaves alternate, simple or pinna, 

 tifid; flowers terminal. 



Species. 1. C. Cvanns. (Blue-bottle). Not very com- 

 monly naturalized. 2. nigra. 3. jacea. 4. benedicta. 5: 

 calcitrapa. All naturalized, not indigenous. 



A vast and compound genus indigenous to Europe, 

 Barbary, Egypt, the Levant and Siberia. In the southern 

 hemisphere only a single doubtful species has been hi> 

 therto discovered by Commerson at Monte Video. 



Order. IV.— POLYGAMIA NECESSARIA. 



(Radial florets ouly fertile.) 



595. CHAPTALIA. Ventenat. 



Calix subinibricated, many-leaved. Feminine 

 ^florets of two kinds, in 2 series, external radiate, 

 internal naked. Discal florets bilabiate. Be- 

 ceptacle naked. Pappus cai)illary. 



Scapes 1 -flowered; leaves radical, entire, usually to- 

 mentose beneath. — Pappus mostly stipitate. 



Species. 1, C ijitegrifolia. Leaves oblong-obovate, re- 

 trorsely denticulate, beneath tomentose; flower nutant. 

 Hab. From Virginia to Florida, nearopen sandy swamps. 

 —Root perennial, fibrous. Leaves covered on the under 

 side with a cotton like tomentum; scape tomentose, much 

 longer than the leaf. Calix oblong, formed of nearly a 

 simple series of leaflets, a few of the external ones short- 

 er. Kays narrow, 15 or 20; external discal florets in a 

 single row, feminine without corolla; internal hermaphro- 

 dite, bilabiate, upper lip 3-toothed, lower bifid. Anthers 

 each conspicuously bisetose at the base. 



An American genus of 7 or 8 species nearly allied to 

 Perdicium, extending to Monte Video. 



