332 CARDUACEAE. 



Bracts broad with a distinct keel or mid-vein, not at all 



foliaceous. 27. EUCEPHALUS. 



Bracts usually narrow, when broad neither keeled nor with a 



prominent mid-vein. 28. ASTER. 



Annuals or biennials, or if short-lived perennials, not with root- 

 stocks ; bracts in many series, with herbaceous spreading or re- 

 flexed tips ; stigma-tips linear to filiform. 



29. MACHAERANTHERA. 

 Stigma-tips triangular or ovate, obtuse or rarely acutish ; bracts not 



foliaceous. 

 Involucres turbinate ; bracts well imbricated in several rows. 



30. LEUCELENE. 

 Involucres hemispherical or broader ; bracts in 1-3 series. 



31. ERIGERON. 



II. Marginal pistillate flowers not ligulate, reduced to a filiform or narrow 



short tube. 33. ESCHENBACHIA. 



B. Heads unisexual, dioecious, discoid; pappus of the staminate flowers with 

 clavate tips. 34. BACCHARIS. 



TRIBE 4. GNAPHALIAE. 



Shrubs; bracts coriaceous; receptacle naked; pistillate flowers numerous; corolla 

 reduced to a short slender tube; hermaphrodite flowers few and sterile; 

 their pappus with clavate tips. 35. BERTHELOTIA. 



Herbs, if at all shrubby only at the base ; bracts more or less scarious. 



Receptacle chaffy; stigmas of the hermaphrodite sterile flowers not truncate. 



36. FILAGO. 



Receptacle not chaffy ; stigmas of the hermaphrodite flowers mostly truncate. 

 Plants dioecious, or the pistillate heads with a few hermaphrodite flowers 



in the center. 



Pappus-bristles of the pistillate flowers falling off in a ring ; those of the 

 staminate flowers clavellate or apically barbellate, crisp ; central 

 hermaphrodite flowers none. 37. ANTENNARIA. 



Pappus-bristles of the pistillate flowers falling off separately ; those of the 

 staminate flowers scarcely clavellate ; central hermaphrodite flowers pres- 

 ent in the pistillate heads. 38. ANAPHALIS. 

 Plants not dioecious; flowers fertile throughout the heads. 



39. GNAPHALIUM. 

 TRIBE 5. HELIANTHEAE. 



A. Bracts not enclosing the achenes of the rays; plants not glandular-viscid. 



I. Disk-flowers hermaphrodite but sterile. 



Marginal pistillate flowers with conspicuous rays ; involucres of very dis- 

 similar sets of bracts. 40. MELAMPODIUM. 



Marginal pistillate flowers reduced to a truncate or obliquely cleft tube; 

 the ligule, if any, reduced to 2 or 3 small teeth. 41. PARTHENICE. 



II. Disk-flowers fertile. 



a. Ray-flowers fertile, with very short tube, persistent on the achenes and 



becoming papery in texture. 



Achenes of the disk compressed ; leaves entire. 42. CRASSINA. 

 Achenes obtusely 4-angled ; leaves toothed. 43. HELIOPSIS. 



b. Ray-flowers deciduous from the achenes or wanting. 



i. Pappus a crown or none, or of a few scales on the angles of the 



achenes and rarely minute ones between, 

 a. Achenes of the disk-flowers not obcompressed (except in RATIBIDA) ; 



chaffs usually more or less concave and clasping. 

 Receptacle conic, subulate or columnar. 

 Achenes 4-angled. 44. BRAUNERIA. 



Achenes quadrangular-compressed; apex of the achenes covered 



by the base of the corolla-tube. 45. GYMNOLOMIA. 



Achenes nearly equally 4-angled ; apex not covered by the base 



of the corolla. 46. RUDBECKIA. 



Achenes flattened, broad-margined or winged. 



47. RATIBIDA. 



