554 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



HELIANTHEAE. 



Involucral scales boat-shaped, each more or less iiiclosing a 

 ray akene. 



Akenes all laterally compressed Madia (p. 575). 



Akenes not laterally compressed. 



Ray akenes turgid, or somewhat obcompressed. 



Involucre 4 or .5-sulcate; disk flower solitar}' ... Hejiizonella (p. 577). 



Involucre not sulcate; disk flowers several Hemizonia (p. 577). 



Ray akenes obcompressed. 



Rays about 5; pappus none Lagophylla (p. 577). 



Rays 8 to 13; pappus capillary Blepharipappus (p. 578). 



Involucral scales not inclosing the outer akenes. 



Pappus present, of well-developed scales or awns. 



Scales of the pappus 12 to 20, thin, fringed Ptilonella (p. 578). 



Scales of the pappus awn-like. 



Awn-like scales 2 or 4, retrorsely l>aiiK'd Bidens (p. 578). 



Awn-like scales 2, subulate Coreopsis (p. 579). 



Pappus wanting, or crown-like, or of short teeth. 



Receptacle elongate-cylindric Rudheckia (p. 579). 



Receptacle flat or convex. 



Rays pistillate and fertile. 



Pappus none Balsamorhiza (p. 580). 



Pappus a toothed crown Wyetiiia (p. 581). 



Rays neutral. 



Akenes flat and thin Helianthem.a (p. 582). 



Akenes prismatic Helianthus (p. 582). 



HELENIEAE. 



Bracts of the involucre in two series: receptacle naked; pap- 

 pus none Jaumea (p. 582). 



Bracts of the involucre in one series. 

 Akenes linear, 4-angled. 



Bracts of the involucre united Eriophyllum (p. 583). 



Bracts of the involucre separate, linear. 

 Heads radiate. 



Pappus scales thin, blunt; viscid pereimial. Hulsea (p. 583). 



Pappus scales awn-like; annual Rigiopappus (p. 583). 



Heads rayless, but marginal flowers enlarged; 



pappus scales blunt, hyaline Chaenactis (p. 583). 



Akenes obpyraniidal. 



Receptacle bristly Gaillardia (p. 584). 



Receptacle naked. 



Akenes 4-5 angled; pappus scales 10 to 20 Hymenopappus (p. 584). 



Akenes 8-10 ribbed; pappus scales 5 or 6 Helenium (p. 584). 



ANTIIEMIDEAE. 



Ray flowers present. 

 Receptacle chafl'y. 



Involucre narrow; rays short Achillea (p. 584). 



Involucre broad : rays conspicuous Antiiemis (p. 585). 



Receptacle naked Chrysanthemum (p. 585). 



Ray flowers none. 



Receptacle conical Matricaria (p. 585). 



