COMPOSITAE (COMPOSITE FAMILY) 773 



+- *- Heads of two kinds, the fertile with a tubcrculate or bur-like involucre. 



40. Ambrosia. Bracts of staminate involucre united; fertile involucre with a single row ol 



tubercles near the summit. Fruiting head 1-seeded. 



41. Franseria. Staminate involucre as in no. 40; fertile involucre with more than 1 row of 



tubercles or prickles. Fruiting head 2-4-seeded. 



42. Xanthium. Bracts of the staminate involucre distinct. Fruiting head 1-4-celled, 1-4-beaked. 



* * * Disk-flowers fertiJo, their corollas funnel-form ; anthers blackish ; pappus none, or a crown 



or cup, or of 1-2 chaffy awns, neither capillary, nor of several uniform chaffy scales ; leaves 

 more commonly opposite. 



+- Eays persistent upon the mature achenes. 



43. Heliopsis. Ray-flowers fertile. Achenes 4-sided. Leaves opposite. 



+- +- Rays deciduous or absent. 

 H- Chaff of the flat receptacle bristle-shaped. 



44. Eclipta. Rays short. Involucral bracts 10-12, in two rows, herbaceous. 



*+ -H- Chaff scale-like, embracing or subtending the achenes. 

 =-- Involucre double ; the outer forming an angled cup. 



45. Tetragonotheca. Outer involucre 4-leaved. Achenes obovoid ; pappus none. 



= = Involucre of one or more rows of separate bracts. 

 a. Receptacle high, conical or columnar in fruit ; pappus none or a short crown or awn. 



46. Rudbeckia. Rays neutral. Achenes 4-sided or terete, flat at the top, rnarginless. 



47. Brauneria. Rays rose-colored (rarely yellow), pistillate, sterile. Achenes short, 4-sided. 



Chaff spinescent. 



48. Lepachys. Rays few, neutral. Achenes flattened laterally and margined. 



49. Spilanthes. Rays yellow or white and fertile, or none. Ray-achenes 3-sided or obcom- 



pressed. 



5. Receptacle flat to convex ; achenes not winged nor very flat. 



50. Borrichia. Achenes8-4-angled ; pappus a short 4- toothed crown. Shrubby. 



51. Helianthus. Achenes flattened, bearing 2 very deciduous chaffy pointed scales and rarely 



minute intermediate ones. 



c. Receptacle convex (rarely conical); achenes flat, compressed laterally, winged or wingless, 

 2-3-awned ; leaves decurrent. 



52. Actinomeris. Bracts few, soon deflexed. Achenes obovate, squarrosely spreading. 



53. Verbesina. Involucral bracts closely imbricated in 2 or more rows. 



* * * * Rays few and neutral, or wanting; achenes obcompressed, i.e. flattened parallel with the 



scales of the involucre (rarely terete) ; involucre double ; the outer spreading and often 

 foliaceous ; receptacle flat ; leaves opposite. 



54. Coreopsis. Involucral bracts distinct or united only at base. Pappus of 2 (or rarely more) 



scales, teeth, or awns, which are naked, not barbed, sometimes obsolete or a mere crown. 



55. Thelesperma. Inner involucre connate to the middle. Achenes terete. Awns 2, retrorsely 



hispid. 



56. Bidens. Involucral bracts distinct or united merely at base. Pappus of 2 or more rigid and 



persistent barbed awns or teeth. 

 ***** Heads radiate or discoid ; disk-flowers all perfect and fertile ; achenes turbinate, 5-angled ; 



pappus of several chaffy scales. 

 +- Leaves alternate, entire ; disk-flowers purplish. 



57. Balduina. Rays numerous, long, neutral. Involucre much imbricated. Receptacle deeply 



honeycombed. 



58. Marshallia. Rays none. Involucre of narrow leafy equal bracts. Receptacle chaffy. 



+- +- Leaves opposite, serrate ; disk-flowers yellow. 



59. Galinsoga. Rays few, short, pistillate, whitish. Involucre of 4-5 thin ovate bracts. Recep- 



tacle chaffy. 



Tribe VI. HELEINEAE. Nearly as Tribe V., but receptacle not chaffy (somewhat so in nos. 6C 

 and 66). In our genera, the disk-flowers perfect and fertile ; the pappus a row of several chaffy 



