WOOTON AND STANDLEY FLORA OF NEW MEXICO. 645 



Bracts of the involucre nearly equal and alike; all dis- 

 tinct. 

 Leaves dissected ; stems leafy throughout. 



115. Rydbergia (p. 730). 

 Leaves entire; stems naked or with only a few leaves. 



116. Tetraneuris (p. 730). 



Tribe VII. ANTHEMIDEAE. 



Receptacle chaffy; rays white. 



Achenes flattened; heads small 117. Achillea (p. 733). 



Achenes terete; heads large 118. Anthemis (p. 733). 



Receptacle naked ; rays white or usually wanting. 



Heads radiate; rays white 119. Chrysanthemum (p. 734). 



Heads discoid. 



Heads corymbose, bright yellow, showy 120. Tanacetum (p. 734). 



Heads not corymbose, not bright yellow, inconspicuous. 



Plants spiny; achenes cobwebby 121. Picrothamnus (p. 734). 



Plants not spiny; achenes not cobwebby 122. Artemisia (p. 734). 



Tribe VIII. SENECIONEAE. 



Involucre of 4 to 6 bracts; stems woody throughout 123. Tetradymia (p. 739). 



Involucre of more than 6 bracts; stems woody at the base or entirely herbaceous. 

 Pappus of plumose bristles; leaves mostly wanting or reduced to scales. 



124. Bebbia (p. 740). 

 Pappus not of plumose bristles; leaves evident. 



Involucral bracts erect-connivent, equal, sometimes with a few short outer 

 ones. 

 Leaves opposite; pappus a single series of rigid bristles. 



125. Arnica (p. 740). 

 Leaves alternate; pappus of numerous soft bristles. 



Heads usually radiate; corollas yellow; leaves bipinnatifid to entii'e. 



126. Senecio (p. 740). 

 Heads discoid; corollas white; leaves thrice pinnatifid into narrow 



segments 130. Mesadenia (p. 749). 



Involucral bracts not erect-connivent, usually unequal and overlapping. 



Leaves opposite, linear-filiform 127. Haploesthes (p. 748). 



Leaves alternate, not linear- filiform. 



Heads homogamous; achenes terete 128. Psathyrotes (p. 748). 



Heads heterogamous; achenes compressed. 



129. Bartlettia (p. 749). 



Tribe IX. CYNAREAE. 



Annual; achenes attached obliquely 131. Centaurea (p. 749). 



Perennials or biennials; achenes not attached obliquely. 

 Leaves prickly; involucral bracts not slender-subulate, 



the tips not hooked 132. Cirsium (p. 749). 



Leaves not prickly; involucral bracts slender-subulate, 



hooked 133. Arctium (p. 753). 



1. VERNONIA Schreb. Ironweed. 



Tall herbaceous perennials with leafy stems and corymbose inflorescence; heads 

 many-flowered, campanulate, the bracts closely imbricated in several series; flowers 

 purple; achenes ribbed, the pappus in two series, the outer of short scales or bristles, 

 the inner long and capillary. 



