638 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Perennials; pappus merely scabrous. 



Receptacle flat 3. Eupatorium (p. 646). 



Receptacle conic 4. Conoclinium (p. 647), 



Pappus at least partly of palese. 



Flowers bluish; involucres many-flowered, campanulate. 



5. COELESTINA (p. 648). 



Flowers pink or white; involucres 3 to 5-flowered, cylindric. 



6. Stevia (p. 648). 

 Achenes 8 to 10-striate or costate. 



Bracts of the involucres herbaceous, not striate nor nerved. 



Shrub; leaves opposite; pappus paleaceous-aristiform. 



7. Carpochaete (p. 648). 



Herbs; leaves alternate; pappus of plumose or barbellate bristles. 



8. Laciniaria (p. 649). 



Bracts of the involucres not herbaceous, conspicuously striate-nerved. 



Pappus plumose; leaves mostly alternate 9. Kuhnia (p. 649). 



Pappus barbellate or scabrous; leaves alternate or opposite. 



10. COLEOSANTHUS (p. 650). 



Tribe III. ASTEREAE. 



Heads unisexual, discoid; plants dioecious 30. Baccharis (p. 671). 



Heads not unisexual, discoid or radiate; plants not dioecious. 

 Marginal pistillate flowers not ligulate, reduced to a filiform or short tube. 



31. ESCHENBACHIA (p. 673). 



Marginal pistillate flowers, if present, ligulate. 

 Ray flowers blue, pink, or white, never yellow. 



Pappus coroniform; rays white 42. Aphanostephus (p. 691). 



Pappus at least in part of awns or bristles; rays of various colors. 

 Pappus of a few long awns or coarse bristles or in ray flowers reduced to paleae. 



43. TOWNSENDIA (p. 691). 

 Pappus of numerous capillary bristles, at least in the disk achenes. 

 Rays only slightly if at all exceeding the pappus; annuals. 

 Bracts in 2 or 3 rows, the outer foliaceous; stigma tips acute. 



34. Brachyactis (p. 682). 

 Bracts in 1 or 2 series, nan'ow, not foliaceous; stigma tips obtuse. 



32. Leptilon (p. 673). 

 Rays conspicuously exceeding the pappus, usually equaling or exceeding 

 the width of the disk (rarely wanting); annuals or perennials. 

 Pappus wanting or a mere trace in the ray flowers. 



41. PSILACTIS (p. 690). 

 Pappus present and usually similar in both ray and disk flowers. 

 Stigma tips triangular or ovate, obtuse or rarely acutish; bracts not 

 foliaceous. 

 Involucres turbinate; bracts imbricated in several rows; rays white. 



40. Leucelene (p. 690). 

 Involucres hemispheric or broader; bracts in 1 to 3 rows; rays white 



to purple 33. Erigeron (p. 674). 



Stigma tips lanceolate or oblong to filiform; bracts often foliaceous. 

 Annuals or biennials, without rootstocks; bracts in many series, 

 with herbaceous spreading or filiform tips. 



39. Machaeranthera (p. 687). 

 Perennials, with rootstocks or caudices; bracts various. 

 Plants with axillary spines; leaves of stems scalelike or wanting. 



38. Leucosyris (p. 686). 



