640 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Leaves entire or toothed, the teeth never spine-tipped. 

 Bracts of the involucre longitudinally striate. 



22. Oligoneuron (p. 666). 

 Bracts not longitudinally striate. 

 Plants low, cespitose, with short woody stems; leaves evergreen; 



heads solitary, long-pedunculate 23. Stenotus (p. 666). 



Stems wholly herbaceous; leaves not evergreen; inflorescence 

 various. 

 Bracts, at least the outer, foliaceous or with prominent folia- 

 ceous tips. 

 Disk flowers tubular; plants with tap-roots. 



24. Pyrrocoma (p. 667). 

 Disk flowers widened upward ; plants not with tap-roots. 

 Heads corymbose; rays few; plants tall. 



25. Oreochrysum (p. 667). 

 Heads solitary; rays numerous; plants low. 



26. Tonestus (p. 667). 

 Bracts not foliaceous, or merely with green tips. 



Rays more numerous than the disk flowers; receptacle fim- 



briolate; heads corymbose 27. Euthamia (p. 667). 



Bays not more numerous than the disk flowers; receptacle 

 alveolate; inflorescence various. 

 Inflorescence racemose or paniculate; bracts not in ver- 

 tical rows; basal leaves not rigid nor sharp-pointed. 



28. Solidago (p. 668). 

 Inflorescence corymbose; bracts in distinct vertical rows; 

 basal leaves rigid, sharp-pointed. 



29. Petradoria (p. 671). 



Tribe IV. GNAPHALIEAE. 



Plants not woolly, tall, usually 1 meter or more. 



Stems woody; leaves sericeous; pappus bristles of sterile flowers with thickened 



tips 44. Berthelotia (p. 693). 



Stems herbaceous; leaves not sericeous; pappus bristles not thickened at the tips. 



45. Pluchea (p. 693). 

 Plants woolly, much less than 1 meter high, seldom more than 40 cm. 

 Receptacle chaffy. 



Bracts of the receptacle inclosing the achencs and falling with them, hyaline- 



appendagod 46. Stylocline (p. 693). 



Bracts merely subtending the achenes, persistent, not hyaline-appendaged. 



47. Evax (p. 693). 

 Receptacle naked. 



Plants not dioecious; flowers fertile throughout the heads. 



48. Gnaphalium (p. 694). 



Plants dioecious or the pistillate heads with a few perfect flowers in the 



center. 



Pappus bristles of pistillate flowars falling separately, those of the stami- 



nate flowers scarcely clavellate; perfect flowers present in the 



centers of pistillate heads 49. Anafhalis (p. 695). 



Pappus bristles of pistillate flowers falling in a ring, those of the staml- 

 nate flowers clavellate; central perfect flowers none. 



50. Antennaria (p. 695). 



