125. CoMPOsiTAE 267 



51. Senecio L. — Rasiwort 



1. Basal k'a\'es crenate, dentate, or entire, the median stem-leaves 



often pinnatifid; stems leafy below, the median and upper 



leaves much reduced; plants perennial. 



2. Basal leaves with winoed petioles; bluffs and o[)en woods, not 



common; C^hampaign. C:iark, and Vermilion counties. Apr.- 



June. 111. plants belong to var. rotundus Britt 



-- - S. ohovatus Muhl. 



2. Basal leaves slender-petioled. 



3. Basal leaves oblanceolate to o\al, not cordate. 



4. Leaves and stems more or less floccose-tomentose, especially 

 at the nodes, only tardily glabrate; peduncles tomentose; 

 in\'olucrej 6-3 mm high, tomentose at base; prairie soil, 

 and in dry ground in oak woods, locally throughout 111. 



May-June. Prairie Ragwort S. plattensis Nutt. 



4. Leaves glabrous or nearly so; stem glabrous, or slightly 

 floccose when young; peduncles glabrous or nearly so; 

 in\olucres 4-5 mm high, glabrous or nearly so; road- 

 sides and open woods in the northern two-thirds of the 



state. May-June. [.S". balsaniitae Muhl.] 



S. pan per cuius Michx. 



3. Basal leaves more or less cordate or subcordate, long-peti- 

 oled, mostly glabrous; wet ground, locally throughout 111. 



Golden Ragw^ort [S. semicordatus Mack. & Bush] 



S. aureus L. 



1. Leaves all pinnatifid or coarsely sinuate-dentate; stems nearly 



equally leafy throughout; plants annual. 



5. Rays 6-10 mm long; bracts not black-tipped; in fields, and 



in moist ground along streams, central and southern 111., 



extending northward to Peoria Co. Apr.-June. Butterweed 



[S. lobatus Pers.] S. glabellas Poir. 



5. Rays none or up to 3 mm long; bracts often black-tipped. 

 6. Stems glabrous at maturity ; bracts black-tipped ; rays none ; 

 waste places, occasional; nat. from Eur. June-July. 



Groundsel S. vulgaris L. 



6. Stems glandular-hairy; bracts not black-tipped; rays about 

 3 mm long; waste ground; nat. from Eur. July-Sept. 

 S. viscosus L. 



Tribe 1 1 . Cynareae 

 52. Arctium L. — Burdock 

 1. Heads 1-2 cm broad, racemose; waste places, common; nat. from 



Eur. July-Sept. Common Burdock A. minus (Hill) Bernu. 



1. Heads 2.5-4.5 cm broad, corymbose. 



2. Petioles solid; heads 3-4.5 cm broad; waste places, occasional; 



nat. from Eur. July-Oct. Great Burdock A. lappa L. 



2. Petioles hollow; heads 2.5-3 cm broad; waste places; nat. from 



Eur.; Cook and Morgan counties. June-Sept 



A. t(>?nrntn\ii!n Mill. 



