1406 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM 



Achenes turbinate; involucre less distinctly graduate 84. TRIDAX. 



Pappus (when present) not of plumose awns or squamellae. 



Achenes subcylindric, about 10 or 15-ribbed 53. VABILLA. 



Achenes not subcylindric, fewer-ribbed. 



Aehenes contracted into a conspicuous stipitiform base. 

 Heads radiate; pappus of 2 awns and several squamellae. 



70. PODACHAENIUM. 



Heads discoid; pappus of 2 awns 71. ACHAENIPODIUM. 



Achenes not contracted into a conspicuous stipitiform base. 



Heads 1 to 5-fiowered; pappus of 10 to 20 unequal paleaceous 



awns 62. ALVORDIA. 



Heads with more numerous flowers, or else (62. Montanoa) 

 pappus wanting. 

 Involucre distinctly double, the outer phyllaries few, herba- 

 ceous, the inner submembranous. 

 Disk achenes (sometimes also the ray achenes) surrounded 

 and included by the convex pales. 



Heads yellow 50. RUMFORDIA. 



Heads white 52. MONTANOA. 



Disk achenes not surrounded and included bj- the pales, 

 these fiat or flatfish. 

 Inner phyllaries connate about to middle. 



79. THELESPERMA. 

 Inner phyllaries essentially free. 



Achenes distinctly rostrate 81. COSMOS. 



Achenes not distinctly rostrate. 



Pappus awns antrorse-ciliate or smooth, rarely want- 

 ing; achenes obcompressed, usually marginate or 



winged 76. COREOPSIS. 



Pappus awns retrorse-hispid (rarely smooth) ; achenes 

 (in our species) linear or subquadrangular, not 



margined or winged 80. BIDENS 



Involucre not distinctly double. 



Achenes obcompressed 77. COREOCARPUS. 



Achenes not obcompressed. 



Pappus of the disk achenes consisting of 4 to many free, 

 usuallj' equal or subequal awns or squamellae. 

 Pappus of deciduous setiform awns. 



64. PERYMENIUM. 

 Pappus of persistent paleaceous awns or squamellae. 

 Achenes obovoid, somewhat compressed; phyllaries 



not indurate 69. HYMENOSTEPHIUM. 



Achenes subterete or 4 or 5-angled; phyllaries indu- 

 rate (the outer sometimes herbaceous) . 



82. CALEA. 

 Pappus of the disk achenes of 2 or 3 awns, with or without 

 squamellae, or a crown of united squamellae, or want- 

 ing. 

 Achenes strongly compressed, fiat or flatfish. 



Pappus of 1 or 2 awns, without squamellae, or want- 

 ing. 

 Achenes winged. 



Pappus awns unequal, the inner broadly winged, 

 the outer usually wingless; involucre gradu- 

 ate, of indurate, usually subherbaceous- 

 tipped phyllaries 67. NOTOPTERA. 



