The Flora of the Cayuga Lake Basin 395 



Involucre not closed nor woody. r.v.i 



c. Heads without rays. 



d. Pappus composed of awns, often barbed 19. Bidens 416 



d. Pappus composed of scales ; involucral bracts hooked, forming a bur. 



31. Arctium 423 

 d. Pappus none or a mere crown (see also 4th c(). 



c. Corollas large, deeply lobed ; flowers pink, purple, or white ; involucral 



bracts usually fimbriate 36. Centaurea 426 



e. Corollas small, dentate ; flowers yellow or yellowish white. 

 /. Receptacle chaffy ; heads large, 1-2 cm. in diam. ; leaves very 



large, thin, and lobed 13. PoLymnia 413 



/. Receptacle naked; heads and leaves smaller, the leaves often 

 dissected. 



g. Heads corymbose, erect 25. Tanacetum 421 



g. Heads paniculate, racemose, or spicate, chiefly nodding. 



26. Artemisia 421 

 d. Pappus capillary. 



e. Involucral bracts scarious throughout ; plants more or less white- 

 woolly. 

 /. Basal leaves much larger than the cauline leaves and differing 



from them in shape 9. Antennaria 408 



/. Basal leaves wanting, or, if present, similar to the cauline leaves. 

 g. Involucre papery-white, the bracts finely striate, spreading. 



10. Anaphalis 411 

 g. Involucre yellowish white or brownish, the bracts subappressed, 



not striate 11. Gnaphalium 412 



e. Involucral bracts not wholly scarious, or, if so, the plants not white- 

 woolly. 

 /. Involucral bracts in one series, often with minute bracts at base. 



g. Plants climbing or twining 2. Mikania 398 



g. Plants not climbing nor twining. 



h. Leaves all basal 28. Petasites 423 



h. Leaves cauline. 



i. Marginal flowers pistillate only; heads 15-20 mm. long. 



29. Erechtites 423 

 i. Marginal flowers perfect; heads 7-10 mm. long.. 30. Senecio 423 

 /. Involucral bracts in 2-many series. 

 g. Foliage spiny. 



/;. Heads 1-flowered, in capitate clusters 32. Echinops 424 



h. Heads many-flowered, distinct. 

 i. Receptacle densely bristly. 



j. Pappus not plumose 33. Carduus 424 



.;'. Pappus plumose 34. Cirsium 424 



i. Receptacle not bristly 35. Onopordum 425 



g. Foliage not spiny. 



h. Corolla deeply lobed; involucral bracts fimbriate or dentate; 



receptacle ibristly 36. Centaurea 426 



h. Corolla merely toothed ; involucral bracts entire ; receptacle 



naked 1. Eupatorium 397 



c. Heads with ray and disk flowers. 

 d. Pappus of awns. 



e. Involucre very glutinous; receptacle not chaffy 3. Grindelia 398 



e. Involucre not glutinous ; receptacle chaffy 19. Bidens 416 



