THISTLE FAMILY 837 



Receptacle not chaffy; style or style-branches of the hermaphrodite flowers mostly 



truncate. 

 Plants dioecious, or the pistillate heads with a few hermaphrodite flowers in the 



center. 



Pappus-bristles of the pistillate flowers falling off in a ring; central hermaph- 

 rodite flowers none. 55. AXTEXXARIA. 

 Pappus-bristles of the pistillate flowers falling off separately; central hermaph- 

 rodite flowers present in the pistillate heads. 56. AXAPHALIS. 

 Plants not dioecious; flowers fertile throughout the heads, hermaphrodite in the 

 middle, surrounded by pistillate ones. 57. GXAPHALJUM. 



Tribe 5. ADEXOCAULEAE. 

 Leaves cordate, white-woolly beneath. 58. ADEXOCAULOX. 



Tribe 6. HELIANTHEAE. 



A. Bracts (at least the outer series) not enclosing the achenes of the rays; plants not 

 glandular- viscid. 



I. Disk-flowers hermaphrodite but sterile. 



Marginal pistillate flowers, with conspicuous rays. 



Achenes not flattened; ligules in ours white; "involucres of very dissimilar sets 



of bracts. 59. MELAMPODIUM. 



Achenes flattened; ligules in ours yellow. 



Ray-flowers in 2-3 series; achenes falling away free. 



60. SILPHIUM. 

 Ray-flowers in 1 series; achenes adnate to 2 or 3 paleae and falling away 



with them. 61. EXGELMAXXIA. 



Marginal pistillate floweis reduced to a truncate or obliquely-cleft tube; the 



ligules, if any, reduced to 2 or 3 small teeth. 

 Acaulescent cespitose perennials; pappus of a pair of lanceolate membranous 



scales. 62. BOLOPHTTA. 



Caulescent annuals; pappus none. 63. PARTHEXICE. 



II. Disk-flowers fertile. 



a. Ray-flowers fertile; the ligules with very short tube, persistent on the achenes 



and becoming papery in texture. 



Achenes of the disk compressed ; leaves entire. 64. CRASSIXA. 



Achenes obtusely 4-angled. 



Leaves toothed; paleae pointless, partly enclosing the achenes. 



65. HELIOPSIS. 



Leaves entire; paleae linear-lanceolate, not enclosing the achenes. ( Kalliac- 

 tis, i. e., B. Carcyana, of) 71. BALSAMORRHIZA. 



b. Ray-corollas deciduous from the achenes or wanting. 



1. Pappus a crown or none, or of a few squamellae on the angles of the achenes, 



and rarely minute ones between. 

 a. Achenes of the disk-flowers not obcompressed (except in Ratibida and 



Ximenesia) : paleae usually more or less concave and clasping. 

 Receptacle conic, subulate or columnar. 

 Achenes 4-angled. 



Ray-flowers purplish or rarely whitish: disk-corollas almost 



without a tube; pappus coroniform. 66. BRAUXERIA. 

 Ray-flowers yellow or none; disk-corollas with a short but mani- 

 fest tube. 



Acbenes quadrangular-compressed; apex of the achenes 

 covered by the base of the corolla-tube. 



67. GYMXOLOMIA. 

 Achenes nearly equally 4-angled; apex not covered by the 



base of the corolla. 68. RUDBECKIA. 



Achenes 5-angled; ray-flowers white. 70. GALIXSOGA. 



Achenes flattened, broad-margined or winged. 



69. RATIBIDA. 

 Receptacle from flat to convex. 



Achenes of the disk neither sharp-angled, margined, nor winged. 

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



plants with thick balsamiferous taproots. 

 Pappus none; stem scapiform or with reduced leave-. 



71. BALSAMORRHIZA. 

 Pappus a lacerate chaffy 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. GYMXOLOMIA. 



Pappus of 2 scarious awns. 73. HELIAXTHUS. 



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 with a callous margin. 



75. EXCELJOPSIS. 

 Plants caulescent; achenes not margined. 



76. HELIAXTHELL.V 



