484 COMPOSITAE (COMPOSITE FAMILY) 



93. Stephanomeria. Involucre double but the outer bracts small-calyculate. Pappus 



plumose. 



++ *+ Achenes beaked. 



94. Tragopogon. Involucre simple, not calyculate. Pappus plumose. 



H- -t- Flowers yellow. 



95. Krigia. Involucre simple. Achenes short-cylindric, with broad truncate summit; 



pappus of both scales and bristles. 



96. Nothocalais. Involucral bracts in 2 series, nearly equal. Achenes fusiform; pappus 



of 10-30 unequal scales (sometimes also some capillary bristles). 



97. Ptilocalais. Involucral bracts imbricated in several series. Achenes linear or turbin 



ate; pappus mostly of scales terminating in a plumose bristle. 



* * Pappus of capillary bristles, never plumose. 

 +- Pappus bristles deciduous together, or 1-8 stouter ones persistent. 



98. Malacothrix. Achenes columnar, 5-15-striate. 



+- -i- Pappus persistent or the bristles falling separately. 

 M- Flowers rose or purplish. 



99. Lygodesmia. Stems nearly leafless. Achenes tapering at summit; pappus white. 



100. Prenanthella. Leaves ample. Achenes ribbed, tapering to the base. Annuals. 



101. Prenanthes. Leaves ample, the cauline in part clasping. Achenes terete or 4-5- 



angled. Perennials. 



++ ++ Flowers yellow, blue, or white. 



= Leaves not all basal; heads several to many, or rarely solitary, 

 a. Achenes not flattened. 



102. Crepis. Achenes tapering upward. Bracts more or less thickened at the base or on 



the midrib at maturity. Pappus white. 



103. Hieracium. Achenes not tapering upward. Bracts not thickened. Pappus sordid 



or fulvous. 



aa. Achenes flattened. 



104. Lactuca. Achenes narrowed upward and often beaked. Involucre cylindraceous. 



105. Sonchus. Achenes truncate at summit. Involucre campanulate. 



= = Leaves all basal; heads solitary on the scapose stems. 



106. Troximon. Achenes smooth at apex, from beakless to long-beaked. 



107. Taraxacum. Achenes spinulose at apex, long-beaked. 



1. VERNONIA Schreb. IRONWEED 



Perennial herbs, with leafy stems and alternate and acuminate or very acute 

 leaves. Flowers perfect, mostly purple, discoid; the heads in corymbose 

 cymes, 15-many-flowered. Involucre much imbricated. Receptacle naked. 

 Achenes cylindrical, ribbed, with double pappus (the outer of minute scale- 

 like bristles, the inner of copious capillary bristles) . 



Leaves conspicuously spinulose-denticulate 1. V. fasciculata. 



Leaves entire or nearly so . . . . . . . . 2. V. Jamesii. 



1. Vernonia fasciculata Michx. Fl. Bor. Am. 2: 94. 1803. Glabrous or 

 nearly so, 6-12 dm. high: leaves thickish, linear to oblong-lanceolate, con- 

 spicuously spinulose-denticulate: heads numerous and crowded on the branches 

 of the compound cyme; involucre (6-8 mm. high) 20-30-flowered ; the bracts 

 all obtuse, or some of the uppermost abruptly mucronate-acute. From 

 Dakota to Texas within the eastern limits of our range, and eastward to the 

 Mississippi States. 



2. Vernonia Jamesii T. & G. Fl. 2: 58. 1842. Glabrous or nearly so, 

 3-5 dm. high: leaves linear-lanceolate or linear, like those of narrowest forms 

 of the last, but smaller and less or obsoletely denticulate : heads few or numer- 

 ous in a loose and open corymbiform cyme, all pedunculate; involucre (8-10 

 mm. high) 15-25-flowered; the bracts all or mostly obtuse. Plains of Ne- 

 braska and Arkansas to Colorado and Texas. 



2. EUPATORIUM L. THOROUGHWORT 



Erect perennial herbs or sometimes shrubby, often sprinkled with bitter 

 resinous dots, and commonly with opposite (sometimes verticillate) leaves. 

 Heads generally corymbose, discoid, 3-many-flowered ; flowers perfect, white, 

 bluish or purple. Involucre cylindrical or campanulate, few-many-flowered. 

 Receptacle naked, flat or conical. Corolla 5-toothed. Achenes, 5-angled, 

 with a single row of slender, capillary, barely roughish bristles. 



