332 CARDUACEAE. 



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



foliaceous. 27. Eicephalus. 



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. Eschenhachia. 



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. 



