264 ASTER FAMILY 



(a) Bracts more or less densely cobwebby, 



not imbricated in rows ; heads yellow- 

 ish ; leaves white woolly to nearly 

 smooth C. hookeridmu 



(b) Bracts not cobwebby 



x. All bracts tipped with spines, cotton}- ; 



heads dark purple; weeds C.lanceoldtus 



y. 'Inner bracts, and sometimes the outer 

 also, pointed but not spiny ; heads 

 white to rose-purple 

 (x) Bracts spreading or reflexed, dense- 

 ly white-woolly ; leaves densely 

 white-woolly . C. neo-mexicdnus 



(y) Bracts not spreading or reflexed, or 

 at the tips only ; bracts not dense- 

 ly white-woolly ; stem simple, 

 branched or none C. Drummondii 



(2) Bracts with a sticky ridge, line or spot on 

 the back, closely imbricated in several 

 rows 



(a) Heads yellowish or yellow C. plattensis 



(b) Heads rose to purple, rarely white C. unduldtus 

 2. Heads less than 1 in. high, dioecious ; weed C. arvensis 



Chaenactis DeCandolle 1836 

 (Gr. chaino, to gape, actis, ray, from the enlarged throat of the corolla) 



Heads without rays, but the marginal flowers somewhat enlarged, 

 often simulating rays, disk-flowers yellow, white or purplish, achenes linear, 

 4-angled or flattened, pappus of scales ; receptacle flat, without chaff, in- 

 volucre bell-shaped to hemispheric ; heads solitary or in cymes ; leaves 

 alternate, usually pinnately-dissected ; annual or perennial. 



1. Marginal flowers manifestly enlarged, becoming 



unequally 5-lobed or ray-like ; pappus of 4 



scales C . stevioides 



2. Marginal corollas not enlarged and irregular; 



pappus of 8-14 scales C. Dougldsii 



Chrysanthemum Linne 1753 Ox-eve Daisy, White Weed 

 (The Greek name, meaning Golden Flower) 



Heads with white pistillate rays, disk-flowers yellow, perfect, achenes 

 roundish or angled, 5-10-ribbed, pappus none or a cup of scales ; receptacle 



