THISTLE FAMILY 839 



Annuals; leaf-segments filiform or nearly so. 



95. CEPHALOBEMBDC. 



Foliage not impressed-punctate ; leaves alternate. 

 Bracts obqvate, cuneate or oblanceolate. 



Perennials with a woody caudex; leaves entire; pappus of 



10 squamellae. 93. PLATYSCHKUHRIA. 



Annuals; leaves dissected; pappus wanting. 



92. AMAUEIOPSIS. 

 Bracts linear. 



Bracts in one row or two subequal rows ; plant not fleshy ; 



achenes linear. 

 Heads radiate, but ligules inconspicuous; pappus of 



opaque squamellae. 99. BlGIOPAPPDS. 



Heads discoid; pappus of hyaline squamellae. 



Achenes angled; squamellae with strong midribs. 



100. CHAMAECHEXACTIS. 



Achenes scarcely angled; squamellae not conspicu- 

 ously ribbed. 101. CHAENACTIS. 

 Bracts in 2-3 rows; heads radiate; leaves more or less 



fleshy. 94. HULSEA. 



Achenes obpyramidal, not 4 times as long as broad. 



Bracts of the involucres erect, not spreading nor reflexed. 



Involucres many-flowered; pappus present; achenes tapering 



below. 



Bracts of the involucres nearly equal and similar, all distinct. 

 Bracts few; corolla flesh-colored; rays wanting. 



100. CHAMAECHAEXACTIS. 



Bracts numerous; corollas yellow; rays usually present. 

 Leaves entire; squamellae short, obtuse or abruptly 



contracted into a point. 105. TETRAXEURIS. 

 Leaves pinnatifid; squamellae linear-lanceolate, at- 

 tenuate but not awn-tipped. 



106. RYDBERGIA. 

 Outer bracts united below; leaves usually pinnatifid with 



narrow divisions. 107. HYMEXOXYS. 



Involucres few-flowered; pappus wanting; achenes linear, 8-10- 



striate. 108. FLAVERIA. 



Bracts of the involucres spreading or reflexed. 



Leaves not decurrent on the stem; tubes of the disk-flowers 



moderately long. 109. DUGALDIA. 



Leaves decurrent on the stem; tubes of the disk-corollas very 



short or reduced to a ring. 110. HELEXIUM. 



2. Receptacle* with bristle-like chaffs. 



Involucral bracts spreading or reflexed. 111. GAILLARDIA. 



Involucral bracts erect. 101. CHAENACTIS. 



Tribe 8. TAGETEAE. 



Bracts of the involucres more or less united; style-branches of the disk-flowers elongate. 

 Bracts of the involucres united only at the base; style-branches with conical tips; 



squamellae of the pappus many-aristate. 112. BOEBERA. 



Bracts of the involucres united into a cup ; style-branches obtuse. 



113. THYMOPHYLLA. 

 Bracts of the involucres distinct; style-branches very short, obtuse, without an appendage. 



114. PECTIS. 



Tribe 9. ANTHEMIDEAE. 

 Receptacle chaffy. 



Achenes flattened; involucres campanulate or obovoid, small; ligules short and broad. 



115. ACHILLEA. 

 Achenes terete, at least not flattened; involucres hemispherical, large; ligules elongate. 



Ray-flowers fertile; paleae of the receptacle membranous, subtending all the 



flowers. 116. AXTHEMIS. 



Ray-flowers neutral; paleae of the receptacle subulate, stiff, subtending only the 



inner disk-flowers. 117. MARUTA. 



Receptacle naked or merely pubescent. 



Heads radiate; achenes 5-10-ribbed all around. 



Ligules white, flat, spreading, longer than the disk-corollas. 



119. LEUCAXTHEMUM. 

 Ligules yellow, concave, erect, not longer than the disk-flowers. 



120. TAXACETUM. 

 Heads in ours discoid; achenes 2-5-ribbed. 



Anthers obtuse. 



Heads solitary, peduncled; flowers in our species all alike (the ray-flowers 



found in other species lacking). 118. CHAMOMILLA. 



Heads in contracted panicles or glqmerules, or in one species solitary; flowers 



of two kinds, the marginal pistillate, but without ligules. 



121. SPHAEROMEKIA. 

 Anthers with pqinted tips; heads racemose, rarely solitary; marginal pistillate 



flowers without ligules. 



Plants spiny; achenes and corollas cobwebby. 122. PlCROTHAMNUS. 



Plants not spiny; achenes not cobwebby. 123. ARTEMISIA. 



