196 Order CAMPANULALES 
In dry soil in the western part of the state. Belmont; Freeport; 
Hat Creek basin; Pine Ridge; Sidney. 
3. Senecio plattensis Nutt. 
On prairies throughout the state. Callaway; Dawson; Ewing; Fair- 
bury; Lincoln; Naponee; Plainview. 
4. Senecio pauperculus Michx. 
Senecio balsamitz Muhl. 
In prairies throughout the state. Emerson; Nebraska City. 
5. Senecio densus Greene. 
Senecio compactus (A. Gray) Rydb. 
In dry prairies in the western part of the state. Callaway; Long 
Pine; Minden; Sheridan county; Thedford; Valentine. 
6. Senecio spartioides T. & G. 
In dry soil in the western part of the state. Chradon; Harrison; 
7. Senecio riddellii T. & G. 
Senecio fremontii (T. & G.) Rydb. 
In dry soil in the western part of the state. Callaway; Crawford; 
Brown county; Lawrence Fork; Valentine. ~ 
Tribe 10. CYNAREA. 
Involucral bracts hooked at the tip; leaves not bristly. 1. Arctium. 
Involucral bracts not hooked at the tip. 
Leaves very spiny. 2. Carduus. 
Leaves not spiny. 3. Centaurea. 
1. Arctium. 1029. 
1. Arctium minus Schk. Common Burdock. 
Introduced in the eastern part of the state. Crete; Lincoln; Peru; 
Talmage. , 
2. Carduus. 1030. 
Thistles. 
Bracts of the involucre, at least the outer, strongly prickly pointed, 
heads all with perfect flowers, over 25 mm. broad. 
All the involucral bracts prickly pointed. 1. C. lanceolatus. 
Inner bracts of the involucre merely acuminate or appendaged. 
Leaves glabrous, hispid or floccose above, tomentose beneath. 
Leaves entire or lobed, the lower sometimes pinnatifid. 
2. C. altissimus. 
Leaves deeply pinnatifid into linear or lanceolate segments. 
Leaves floccose but green above, strongly spiny. 
3. C. flodmanii. 
Leaves glabrous above, weakly spiny. 4. C. discolor. 
Leaves tomentose on both sides, or becoming glabrous above. 
Leaves pinnatifid. 
Spines of involucre as long as the bracts, yellow. 
Flowers pink or purple. 5. C. undulatus. 
Flowers yellow. 6. C. plattensis. 
Spines of involucre as long as the bracts, yellow. 
7. C. ochrocentrus. 
Leaves entire or undulate. 8. C. nebraskensis. 
Bracts of the involucre not strongly prickly pointed; heads small, 
not over 25 mm. broad; dicecious. 9. C. arvensis. 
