CL. XIX.] SYNGENESIA. 305 



** Corollas of the marginal florets strap-shaped. 



36. BE'LLIS. Receptacle naked, conical. Seed-down none. Calyx 



hemispherical ; scales equal. Seed inversely egg-shaped. 



39. MATRICA'RIA. Receptacle naked, nearly cylindrical. Seed- 



down none. Calyx hemispherical or nearly plane, imbricated ; the 

 scales membranous on the edges. 



37. CHRYSANTHEMUM. Receptacle naked, a little convex. Seed- 



down none. Calyx hemispherical, imbricated; the scales with a 

 dilated membranous border. 



38. PYRE'THRUM. Receptacle naked. Seed crowned with a mem- 



branous border. Calyx hemispherical, imbricated ; the scales 

 rather acute, membranous at the edges. 



35. DORO'NICUM. Receptacle naked. Seed-down simple, wanting 

 on the seeds of the rays. Calyx a double row of equal scales, 

 longer than the disk. 



33. I'NULA. Receptacle naked. Seed-down simple. Calyx hemi- 



spherical, imbricated. Marginal florets very numerous, linear. 

 Anthers with two bristles at the base. 



27. ERI'GERON. Receptacle naked. Seed-down simple. Calyx im- 



bricated. Marginal florets numerous, linear, very narrow. An- 

 thers without bristles. 



32. SOLIDA'GO. Receptacle naked, pitted. Seed-down simple. Calyx 

 imbricated, its scales close. Marginal florets about five. 



31. A'STER. Receptacle naked. Seed-down simple. Calyx imbricated, 

 the lower scales spreading. Marginal florets more than ten. 



30. SENE'CIO. Receptacle naked. Seed-down simple. Calyx double ; 

 the inner cylindrical, of equal scales ; the outer of several minute 

 ones ; all the scales withered-looking at the tip. 



28. TUSSILA'GO. Receptacle naked. Seed-down simple. Calyx 



simple, swelled at the base ; scales numerous, equal, somewhat 

 membranous. Corolla rayed. 



29. PETASI'TES. Receptacle naked. Seed-down simple. Calyx egg- 



shaped, imbricated with two rows of lanceolate scales. Florets 

 tubular. 



34. CINERA'RIA. Receptacle naked. Seed-down simple. Calyx sim- 



ple, cylindrical ; scales numerous, equal. Seed four-cornered. 



40. ANTHEMIS. Receptacle convex, chaffy. Seeds crowned with a 



membranous border. Calyx hemispherical ; its scales nearly equal, 

 their margins membranous. 



41. ACHILLE'A. Receptacle flat, chaffy. Seed-down none. Calyx 



egg-shaped, imbricated ; the scales unequal. Marginal florets 

 few, roundish. 



(Bidens cernna.) 



Order III. POLYGAMIA FRUSTRANEA. 



Florets of the disk perfect and fertile ; those of the circum- 

 ference destitute of both stamens and pistil. 



42. CENTAURE'A. Receptacle bristly. Seed-down simple or feathery. 



Calyx imbricated. Marginal florets funnel-shaped, dilated, irre- 

 gular. 



