30 VASCULAR PLANTS. 



flat, paleaceous. Akenes flattened; pappus 2, 

 marginal, persistent, aristae ; alternating with 2 

 caducous paleae. 



% . flowers yellow. 



29. Helianthus, L. 



Frustranea. Head oc-flowered. Receptacle 

 flat, paleaceous. Akenes slightly compressed 

 (quadrangular); pappus 2, marginal, caducous, 

 palefe with minute, intermediate ones. 



. IX. ray-flowers yellow. 



b. Palece deciduous. 



30. Pugiopappus, Gray. 



Saperflua. Head cc-flowered ; ray-flowers 

 broad, deeply crenate. Involucre 2-seriate. 

 Pappus of the disk 0; of the ray 2 arista:. 



. flowers yellow ; leaves alternate. 



31. leptosyne, DC. 



Superflua. Head oc-flowered ; rays broad, 

 deeply crenate. Involucre 2-seriate. Pappus 0. 

 0. flowers yellow. 



32. Bidens, L. 



Frnstanea. iEqualis. Head oo-flowered. In- 

 volucre 2-seriate. Pappus 2 — 4, echinate aristae. 



0. 71. flowers yellow, white; leaves opposite. 



