1000 



COMPOSITAE 



Cirsium 



3o 

 Map 2193 



Carduus nutans L 



Leaves and flowers not as above. 



Largest involucres usually not more than 13 mm wide; leaves glabrous above and 

 beneath or woolly beneath and tardily glabrous; perennial with deep, creep- 

 ing rootstocks. 



Leaves more or less deeply pinnatifid 3. C. arvense. 



Leaves of stem sinuate-pinnatifid, somewhat ruffled; leaves of branches sub- 

 entire or dentate, minutely spinose 3a. C. arvense var. mite. 



Leaves all glabrous, linear-oblong, lanceolate or obovate, the margins entire or 



setose-spinulose 3b. C. arvense var. integri folium. 



Leaves denticulate, lower surface white-tomentose; peduncles lanate 



3c. C. arvense var. vestitum. 



Largest involucres usually more than 13 mm wide; lower surface of the leaves 



tomentose; plants without deep, creeping rootstocks. 



Plants low and very stout, mostly 3-6 dm high; heads usually 1-3, rarely 5, very 



large; involucres 4-6 cm wide and about 4 cm high; tips of inner in- 



volucral bracts crisped, dilated, pubescent, with laciniate-ciliate margins; 



plants flowering mostly from June 12 to July 28, flowers mostly Purplish 



Lilac (Ridgway Standard) 4. C. Hillii. 



Plants generally taller; heads smaller and more numerous. 



Tips of outer involucral bracts not prickly, sometimes with a mucro about 0.5 



mm long 5. C. muticiim . 



Tips of outer involucral bracts prickly, the tips usually 2-8 mm long. 



Heads on long, bracted peduncles; peduncles mostly 1-4 dm long; involucral 



bracts more or less scabrous 6. C. virginianvm. 



Heads terminating leafy branches; peduncles short, less than 1 dm long. 

 Leaves deeply pinnatifid, with linear-lanceolate lobes; leaf-margins rev- 



olute 7. C. discolor. 



Leaves entire or sparingly sinuate-lobed, or the basal ones sometimes 

 deeply pinnatifid; leaf -margins generally flat 8. C. altissimum. 



1. Cirsium vulgare (Savi) Airy-Shaw. (Fedde Rept. Spec. Nov. 43: 

 302-315. Apr. 15, 1938.) (Cirsium lanceoMum (L.) Hill of Indiana 

 authors.) Bull Thistle. Map 2194. This species is biennial. It no 

 doubt has become established in every county of the state. It formerly 

 was common in pastures and clearings, and frequent along roadsides and 

 in fields, open woodland, and waste places. As nearly as I can remember, 

 about 25 years ago it began to disappear, and in a few years it had prac- 



