THISTLE FAMILY 229 



Achenes flattened, broad-margined or winged. 



69. R.^TIBIDA. 

 Receptacle from flat to convex. 



Achenes of the di.sk neither sliarp-angled, margined, nor winged. 

 Rays fertile, their achenes commonly 3-angled or obcompressed : 

 plants with thick balsamiferous taproots. 

 Papptis none; stem scapiform or with reduced leaves. 



71. B.\LS.\MORRHIZA 



Pappus a lacerate chafify crown or of distinct squamellae; 

 stem low but leafy. 72. Wyethia. 



Rays sterile or wanting; plants not with fleshy taproot. 

 Pappus none or a minute ring. 67. Gymnolomia. 



Pappus of 2 scarious awns. 73. Hf,li.\nthus. 



Achenes of the disk thin-edged, margined or winged. 

 Ray-flowers neutral; achenes scarcely winged. 



Pappus none or an awn to each angle of the achenes. 



74. EXCELIA. 



Pappus of small teeth between the 2 or more awns or scales 

 over the angles of the achenes. 

 Plants scapose; achenes witli a callous margin. 



75. EXCELIOPSIS. 



Plants caulescent; achenes not margined. 



76. Helianthella. 

 Ray-flowers fertile; achenes winged; pappus-awns without inter- 

 mediate scjuamellae. 77. Ximene-sla.. 



b. Achenes obcompressed; paleae flat or hardly concave; involucres dis- 

 tinctly double. 

 Bracts of the involucres distinct or nearly so. 



Pappus in ours of small teeth, a mere border, or wanting. 



78. Coreopsis. 

 Pappus of 2-4 barbed or hispid awns. 79. Bidexs. 



Bracts of the inner involucre tmited at least to near the middle. 



80. Thelesperma. 

 2. Pappus of 5-many, linear to lanceolate squamellae with thickened axis and 

 hyaline margins. 

 Rays fertile; paleae of the receptacle thin and scarious; pappus-sq-uamellae 



fimbriate. 81. Ptiloxell.\. 



Rays sterile; paleae of the receptacle bristle-form; pappus-squamellae not 

 fimbriate. 110. Gaillardia. 



B. Bracts of the involucres uniserial, partly or wholly enclosing the achenes of the fer- 

 tile ray-flowers; plants glandular- viscid. 

 • Achenes of the inconspicuous rays laterally compressed and enclosed in the con- 

 dupUcately infolded involucral bracts. 

 Disk-flowers several; corolla hairy; stout annuals vrtth sessile or short-pedimcled 



heads. 82. AIadia. 



Disk-flowers solitary; corolla glabrous; slender low annuals with small heads on 

 filiform pedmicles. 83. H.vrp.vecarpus. 



Achenes of the ray-flowers with broad and rounded backs, or more commonly obcom- 

 pressed. 

 Ligules of the ray-flowers miniite; achenes completely invested by the whole 

 involucral bract; disk-flowers soUtary; heads small and short-peduncled. 



84. He.mizoxella. 

 Ligules of the ray-flowers conspicuous; achenes enclosed in the basal portion of 

 the bracts, the dilated margins of which are abruptly infolded; disk-flowers 

 several or many. 

 Ray-flowers about 5, ^vith deeply 3-cleft ligules; disk-flowers sterile, without 



pappus. 85. Lagophylla. 



Ray-flowers 8-20, with merely 3-lobed or toothed ligules; disk-flowers mostly 

 fertile ^vith pappus of 5-20 bristles. 86. Bleph.\ripappus. 



Tribe 7. HELENIAE. 



I. Ligules persistent and becoming papery on the striate achenes; plants more or less 

 woolly. 

 Pappus of scales; rays 3-4, very broad; involucres of 4-10 coriaceous woolly bracts. 



87. P.SILO.STROPHE. 



Pappus none; rays 5-50; involucres of numerous thin herbaceous bracts. 



88. Baileya. 

 IL Ligules deciduous or none. 



A. Achenes flat with only marginal nerves; disk-corollas 4-toothed. 

 Pappus none or of a single bristle; bracts distmct; suflruticose plants. 



89. MOXOTHRIX. 



Pappus of a lacerate-ciliate crown and sometimes with an additional pair of short 

 awns; bracts more or less connate; not suffi'uticose plants. 



90. Pericome. 



B. Achenes angled, not flat, nerved or striate. 

 1. Receptacle naked. 



a. Bracts of the involucres pale or colored, at least the margins and tips scari- 

 ous. 

 Corollas of the disk-flowers with reflexed or spreading lobes; bracts of the 

 broadly campanulate involucres obovate or broadly oblong. 

 Heads discoid. 96. Hy.me.xopappus. 



Heads radiate; Ugules obscurely toothed, yellowish or white. 



97. Leuc.wipyx. 



