THISTLE FAMILY 839 



Annuals; leaf-segments filiform or nearly so. 



^ ,. ^ . , 95. CEPHALOBEMBIX. 



l<oiiage not impressed-pimctate; leares alternate. 

 Bracts obovate, cuneate or oblanceolate. 



Perennials with a woody caudex; leaves entire: pappus of 



10 squaraellae. 93, PK\TyscHKUHRiA. 



Annuals; leaves dissected; pappus wanting. 



^ ^ ,. 92. Amaukiopsis. 



Bracts Imear. 



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



achenes linear. 



Heads radiate, but ligules inconspicuous; pappus of 

 opaque squameilae. 99. Rigiopapfus. 



Heads discoid ; pappus of hyaUne squameilae. 



Achenes angled; squameilae vrith strong midribs. 



. , 100. Chamlieciienactis. 



Achenes scarcely angled; squameilae not conspicu- 

 ously ribbed. 101. Chaenactis. 

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

 . , , fleshy. 94. Hulska. 

 Achenes obpyramidal, not 4 times as long as broad. 



Bracts of the involucres erect, not spreading nor reflexed. 



^ Involucres many-flowered; pappus present; achenes taperins 



below. 



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

 Bracts few; corolla flesh-colored; rays wanting. 



100. CH.\MAECHAENACTI3. 



Bracts numerous; corollas yeUow; rays usually present. 



Leaves entire; squameilae short, obtuse or abruptly 

 contracted into a point. 105. Tetraneuris. 



Leaves pinnatifld; squameilae hnear-lanceolate, at- 

 tenuate but not awn-tipped. 



106. Rydberglv. 

 Outer bracts imited below; leaves usually pinnatifld with 

 narrow divisions. 107. Hymenoxys. 



Involucres few-flowered; pappus wanting; achenes Unear, 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 decin-rent 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. Gatll.\rdta. 



Involucral bracts erect. ' 101. Ch.aexactis. 



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; 



squameilae of the pappus many-aristate. 112. Boebera. 



Bracts of the involucres imited 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. 

 Eeceptacle 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. Anthemis. 



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



inner disk-flowers. 117. M.\ruta. 



Receptacle naked or merely pubescent. 



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



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



119. LEUCANTHEMtTM. 



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



120. Tanacetum. 

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

 Anthers obtuse. 



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



fo\md in other species hacking). 118. Ch.\momilla. 



Heads in contracted pamcles or glomeruies, or in one species solitary; flowers 

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



121. SPHLVEROMERLi. 



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



flowers without Mgules. 

 Plants spiny; achenes and corollas cobwebby. 122. Picroth.a^inus. 



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



