THISTLE FAMILY 839 



Annuals; leaf-segments filiform or nearly so. 



95. Cephalobembix. 

 Foliage not impressed-punctate; leaves alternate. 

 Bracts obovate, cuneate or oblanceolate. 



Perennials with a woody caude.x; leaves entire; pappus of 



10 squamellae. 93. Pl.\tyschkuhria. 



Annuals; leaves dissected; pappus wanting. 



92. Amauriopsis. 

 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. Rigiopappus. 



Heads discoid; pappus of hyaline squamellae. 



Achenes angled; squameUae with strong midribs. 



100. CH/ViL\.ECHENACTIS. 



Achenes scarcely angled; squameOae not conspicu- 

 ously ribbed. 101. Ch.vexacti.s. 

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

 fleshy. 94. HULSE.v. 

 Achenes obpyramidal, not 4 times as long as broad. 



Bracts of the involucres erect, not spreading nor refle.xed. 



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. CH.\M.\ECH.AENACTI3. 



Bracts numerous; corollas yellow; rays u.sually present. 

 Leaves entire; squamellae short, obtuse or abruptly 



contracted into a point. 105. Tetraneuris. 

 Leaves pinnatifld; squamellae linear-lanceolate, at- 

 tenuate but not awn-tipped. 



106. Rydbergl\. 

 Outer bracts united below; leaves usually pinnatifld with 

 narrow divisions. 107. Hymenoxys. 



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

 striate. 108. Flaveria. 



Bracts of the involucres spreading or refle.xed. 



Leaves not decin-rent 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. 1 10. Helenium. 



2. Receptacle with bristle-like chaffs. 



Involucral bracts spreading or reflcxed. 111. Gaill-vrdia. 



Involucral bracts erect. 101. Ch.\enactis. 



Tribe 8. TAGETEAE. 

 Bracts of the involucre.s 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. Thyaiophyll.\. 

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



114. Pectis. 

 Tribe 9. ANTHEMIDEAE. 



Receptacle chafTy. 



Achenes flattened; involucres campanxflate 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. IM.utUT.\. 



Receptacle naked or merely pubescent. 



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



Ligules white, flat, spreading, longer than the dlsk-coroUas. 



119. Leucanthemum. 

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



120. Taxacetum. 

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



Anthers obtuse. 



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



found in other species lacking). 118. Ch.^momilla. 



Heads in contracted panicles or glomerules, or in one species sohtary; flowers 



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



121. Sph.veromerl\. 

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



flowers without hgules. 

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



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



