THISTLE FAMILY 839 



Annuals; leaf-segments filiform or nearly so. 



95. Cephalobembdc. 

 Foliage not impressed-pimctate; leaves alternate. 

 Bracts obovate, cuneate or oblanceolate. 



Perennials with a woody caudex; leaves entire; pappus of 



10 squamellae. 93. Platyschktjhria. 



Annuals; leaves dissected; pappus wajiting. 



92. Amaueiopsis. 

 Bracts linear. 



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

 achenes Unear. 

 Heads radiate, but ligules inconspicuous; pappus of 



opaque squamellae. 99. Rigiopappus. 



Heads discoid; pappus of hyaline squamellae. 



Achenes angled; squamellae with strong midribs. 



100. Chamaechenactis. 

 Achenes scarcely angled; squamellae not conspicu- 

 ously ribbed. 101. Chaenactis. 

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

 fleshy. 94. Hui^EA. 

 Achenes obpyramidal, not 4 times as long as broad. 



Bracts of the involucres erect, not spreading nor reflexed. 



Involuci-es many-flowered; pappus present; achenes tapering 

 below. 

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

 Bracts few; coroUa flesh-colored; rays wanting. 



1 00. CHAMAECHAEN.\CTI3. 



Bracts numerous; corollas yellow; rays usually present. 

 Leaves entire; squamellae short, obtuse or abruptly 



contracted into a pomt. 105. Tetraneuris. 

 Leaves pinnatifld; squamellae Unear-lanceolate, at- 

 tenuate but not awn-tipped. 



106. Rydbergia. 

 Outer bracts miited below; leaves usually pinnatifld with 

 narrow divisions. 107. Hymenoxys. 



Involucres few-flowered; pappus wanting; achenes hnear, 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 decuj-rent on the stem; tubes of the disk-corollas very 

 short or reduced to a ring. 110. Helenium. 



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 imited; 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 myomeres distinct ; style-branches very short, obtuse, without an appendage. 



114. Pectis. 



Tribe 9. ANTHEMIDEAE. 

 Receptacle chaffy. 



Achenes flattened; involucres campanulate or obovoid, small; Ugifles 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. Anthemis. 



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

 inner disk-flowers. 117. Maruta. 



Receptacle naked or merely pubescent. 



Heads radiate; achenes 5-10-ribbed aU arovmd. 



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

 ^. , „ 119. Leucanthemum. 



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

 „ , . ,. . 120. Tanacetxim. 



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

 Anthers obtuse. 



Heads soUtary, pedxmcled; flowers in our species all alike (the ray-flowers 



foimd m other species lacking). 118. Chamomilla. 



Heads m contracted panicles or glomerules, or in one species soUtary; flowers 

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

 , ^, .^, . , 121. Sphaeromeria. 



Anthers with pomted tips; heads racemose, rarely solitary; marginal pistUlate 

 flowers without Ugules. 

 Plants spiny; achenes and corollas cobwebby. 122. PiCROTH.UkiNUS. 



Plants not spmy; achenes not cobwebby. 123. Artemisl-v. 



