GENUS 102. 



THISTLE FAMILY. 



539 



Taller, up to 2 l / 2 high; basal leaves ovate to oblong-lanceolate. 



Densely persistently tomentose; stem-leaves mostly merely dentate. 13. 5". tomentosus. 



Loosely tomentose, booming glabrate ; stem leaves mostly pinnatifid. 14. S. plattensis. 



tt Plants glabrous, or nearly so, at least when mature, the stem sometimes tomentose at the base. 



Basal leaves or some of them deeply cordate. 



Basal leaves lanceolate or oblong-lanceolate. 15. S.Robbinsii. 



Basal leaves orbicular to ovate. 16. S. aureus. 



None of the leaves cordate. 



At least the stem-leaves lobed, laciniate, or pinnatifid ; pubescence, if any, woolly ; basal leaves 



dentate or crenate. 

 Head rayless ; boreal species. 

 Heads radiate. 



Basal leaves obovate to suborbicular. 

 Basal leaves oblong to spatulate. 



Basal leaves oblong to lanceolate, dentate or crenate. 

 Involucre 4" high ; basal leaves sharply serrate. 

 Involucre 2^/2' '-3 1 A" high; basal leaves mostly crenate. 

 Heads few ; basal leaves mostly short. 

 Heads very numerous ; basal leaves long. 



17. S. discoideus. 



1 8. 5". obovatus. 



19. 6". Crawfordii. 



20. S. pauperculus. 



21. S. Smallii. 



Basal leaves linear-cuneate, entire, or few-toothed at the apex. 22. S. densus. 

 All leaves entire or very nearly so ; pubescence, if any, of crisp hairs. 23. S. integerrimus. 



i. Senecio vulgaris L. Common Ground- 

 sel. Fig. 4610. 



Senecio vulgaris L. Sp. PI. 867. 1753. 



Annual, puberulent or glabrate; stem hollow, 

 usually much branched, 6'-i5' high. Leaves pin- 

 natifid, 2'-6' long, the lower spatulate in outline, 

 petioled, obtuse, the upper sessile or clasping at 

 the base, more deeply lobed or incised, their seg- 

 ments oblong, dentate; heads several or numer- 

 ous in the corymbs, nearly 3" broad, 4"-6" high; 

 bracts of the involucre linear, with few or sev- 

 eral subulate black-tipped outer ones; rays none; 

 achenes slightly canescent; pappus white. 



In cultivated ground and waste places, Newfound- 

 land to Hudson Bay, North Carolina, Minnesota, 

 Michigan, and west to the Pacific Coast. Bermuda. 

 Naturalized from Europe. Other names are grinsel, 

 simson, birdseed, chickenweed. April-Oct. 



JL 



2. Senecio sylvaticus L. Wood Groundsel. 

 Fig. 4611. 



Senecio sylvaticus L. Sp. PI. 



1753- 



Annual, glabrous or puberulent ; stem usually much branch- 

 ed, i-2l high, leafy. Leaves pinnatifid, oblong or lanceo- 

 late in outline, the segments oblong or spatulate, obtuse, 

 dentate, lobed or entire, or the uppermost leaves linear and 

 merely dentate ; heads several or numerous in the corymbs, 

 slender-peduncled, about 2" broad, 3"-4" high; involucre 

 usually quite naked and swollen at the base; rays very short 

 and recurved ; achenes canescent ; pappus white. 



In waste places Newfoundland to Nova Scotia, Quebec and 

 Maine. Also on the coasts of California and British Columbia. 

 Naturalized or adventive from Europe. April-Sept. 



