ins 



Pappus caducous; achenes compressed, notched at apex; leaves chiefly or all radical; 



perennial 60. Helianthella. 



B. Bracts of the involucre in 2 dissimilar scries ("double") ; flowers yellow. 

 Leaves opposite, simple or pinnately parted; pappus of persistenl barbed awns.. 61. Bidens. 

 Leaves chiefly radical, or alternate, dissected into narrowly linear or filiform lobes; 

 pappus not of barbed awns 62. Leptosyne. 



Tribe 8. Ambrosieae. Ragweed Teibe. 



Coarse homely weeds with small greenish or white heads. Leaves alternate 

 or the lowest opposite in no. 63. Flowers unisexual, the staminate and the 

 pistillate in separate heads (the staminate heads in a raceme or spike above the 

 pistillate heads, which are few and axillary) or in the same head (heads solitary 

 in the axils). Receptacle of the staminate or of the perfect heads with chaff- 

 like bracts. Rays none. Corolla of pistillate flowers none or a mere rudiment. 

 Anthers distinct or scarcely coherent, not caudate. Pappus none. Fruit com- 

 monly a bur. 



Heads containing both staminate and pistillate flowers, the latter at the margin; involucre 



of 4 or 5 rounded united bracts 63. Iva. 



Heads unisexual, both pistillate and staminate on the same plant; involucre of pistillate 

 heads closed and bur-like, only the style-branches exserted; staminate heads in a 

 raceme or spike, their involucres open. 

 Involucral bracts of the staminate heads united. 



Pistillate involucre beaked at apex and armed near the beak with a single row of 



short prickles 64. Ambrosia. 



Pistillate involucre with 1 to 4 beaks and armed with several rows of prickles 



65. Franseria. 



Involucral bracts of staminate heads distinct; involucre of pistillate heads maturing into 



a stout bur .66. Xanthium. 



Tribe 9. Inuleae. Everlasting Tribe. 



Annual or perennial herbs. Herbage mostly white-woolly (except Pluchea). 

 Leaves alternate (opposite in Psilocarphus), entire, or more or less dentate 

 in Pluchea and Adenocaulon. Heads small; rays none. Bracts of the invol- 

 ucre frequently white or scarious. Pistillate flowers mostly with filiform 

 corollas. Sterile flowers either perfect or staminate. Anthers caudate at base. 

 Style-branches stigmatic to the unappendaged summit. Pappus capillary or 

 none. 



A. Receptacle with bracts (chaffy); involucral bracts few or none; woolly annuals. 

 Fruit-bearing bracts each enclosing its achene and falling away with it. 



Achenes gibbous, the corolla and style borne laterally; pappus none 67. Micropus. 



Achenes straight or only slightly curved, the corolla and style borne at its apex; 

 pappus none. 



Receptacle slender or columnar; leaves alternate 68. Styloclink. 



Receptacle globose; leaves opposite 69. Psilocarphus. 



Fruit-bearing bracts open, merely subtending the achenes, persistent; pappus none 



70. Evax. 



Bracts of 2 kinds, the lower loosely enclosing the pistillate (fertile) flowers, the others 



chaff-like and surrounding a central cluster of both pistillate and sterile flowers 



whose achenes bear pappus 71. Filago. 



B. Receptacle without bracts (not chaffy); involucral bracts many (except no. 75); 



perennials or annuals. 

 Pappus present; achenes naked. 



Bracts of the involucre scarious; herbage woolly. 



Flowers all fertile, perfect and pistillate in the same head 72. Gnaphalium. 



Fowers dioecious 73. Anaphalis. 



Bracts of the involucre dry but not scarious; herbage not woolly 74. Pluchea. 



Pappus none; aelunes bearing stipitate glands; leaves broad, woolly beneath 



75. Adenocaulon. 



Tribe 10. Astereae. Aster Tribe. 

 Annual or perennial herbs or BhrubSj with bland watery juice, scentless 



