184 CAMPANULALES 



3. Bidens comosa (A. Gray.) Weigand. 



In moist soil in the eastern part of the state. Black Island; Jules* 

 burg; Keya Paha; Nebraska City; Newark. 



4. Bidens frondosa L. 



Common in wet soil over most of the state. Red Cloud; Kearney; 

 Kennedy; Lincoln; Nebraska City; Thedford; Valentine. 



5. Bidens bipinnata L. 



Nebraska according to Britton's Manual. 



€. Bidens tricliosperma (Michx. Britton. 



Common in wet soil over most of the state. Black Island; Keya Paha; 



Long Pine; Royal; Thedford. 



7. Bidens aristosa (Michx.) Britton. 

 Long Pine; Nebraska City; Valentine. 



8. Bidens involucrata (Nutt.) Britton. 



In wet soil. Endicott; Falls City; Nemaha. 



11. Thelesperma. 1003. 



Rays large, pappus scales not much longer than the width of the 

 achene. 

 Leaves not rigid, their segments filiform. 1. T. trifidum. 



Leaves rigid, their segments linear or filiform, perennial. 



2. T. Intermedium. 

 Rays small or wanting, pappus awns longer than the width of achene. 



3. T. gracile. 



1. Thelesperma trifidum (Poir.) Britton. 



In dry soil in the western part of the state. Box Butte County; Craw- 

 ford; Long Pine. 



2. Thelesperma intermedium Rydb. 



In dry soil in the western part of the state. Alliance; Crawford. 



3. Thelesperma gracile (Torr.) A. Gray. 



In dry soil, common in the western part of the state. Cherry County; 

 Dismal River; Franklin; Kearney; Red Cloud; Shelton; Thedford; 

 Valentine. 



Tribe 9. AMBROSIAE. 



Staminate and pistillate flowers in the same heads, the pistillate 

 marginal. "I- '^^• 



Staminate and pistillate flowers in separate heads, the pistillate 1-4 in 

 a nut-like or bur-like involucre. 

 Involucre of the staminate heads of united bracts, that of the pistil- 

 late never with hooked bristles. 

 Pistillate involucre 1-flowered, usually armed with 4-8 tubercles or 

 spines in a single series. 2. Ambrosia. 



Pistillate involucre with 1-4 flowers, armed with several to nu- 

 merous prickles in more than one series. 3. Gaertneria. 

 Involucre of the staminate heads of separate bracts; that of the 

 pistillate heads 2-flowered, covered with numerous hooked 

 bristles. 4. Xanthium. 



