772 COMFOSITAE (COMPOSITE FAMILY) 



21. Boltonia Achenes very flat, thick-winged ; pappus of short bristles and usually 2-4 awns. 



+- + Pappus of numerous long and capillary bristles ; receptacle flat. 



22. Aster. Heads many-flowered, on leafy peduncles. Involucral bracts mostly unequal, loosely 



or closely imbricated. Achenes flattish ; pappus simple (rarely double), copious. 



23. Engeron. Heads many-flowered, on naked peduncles. Involucre of narrow equal bracts, 



little imbricated. Achenes flattened ; pappus simple and rather scanty, or with some 

 outer minute scales. 



24. Sericocarpus. Heads 12-20-flowered ; rays 4 or 5. Involucre subcylindric or club-shaped, 



Imbricated, cartilaginous. Achenes short, narrowed downward, silky. 

 * * * Rays none ; heads dioecious (all pistillate or all staminate). 



25. Baccharis. Heads many-flowered. Pappus capillary. Smooth glutinous shrubs. 



Tribe IV. IWtTLEAE. Heads discoid (radiate only in Inula), the pistillate flowers mostly filiform 

 and truncate. Anthers sagittate, the basal lobes attenuate into tails. Style-branches with un- 

 appendaged obtuse or truncate naked tips. Pappus capillary or none. 



* Receptacle flat, naked ; involucre not scarious, imbricated ; not woolly. 



26. Pluchea. Heads containing a few perfect but sterile flowers in the center, and many pistillate 



fertile ones around them. Pappus capillary. 



* * Receptacle chaffy ; involucral bracts few, mostly scarious ; low floccose-woolly annuals ; flowers 



as in no. 26. 



27. Gifola. Receptacle subulate. Achenes terete. Outer flowers without pappus. 



* * * Receptacle naked ; involucral bracts many, scarious ; floccose-woolly herbs. 



28. Antennaria. Heads dioecious. Pappus of sterile flowers club-shaped or barbellate, of the 



fertile capillary, united at base and deciduous together. 



29. Anaphalis. Heads dioecious or nearly so. Pappus not thickened above nor at all united at 



base. 



80. Gnaphalium. Heads all fertile throughout. Pappus all capillary. 



* * * * Heads radiate ; receptacle naked ; involucre herbaceous ; pappus copious. 



81. Inula. Heads large, many-flowered. Flowers yellow. Stout perennial. 



***** Corollas all somewhat broadly tubular and lobed ; involucre not scarious ; receptacle naked ; 



pappus none. 



82. Adenocaulon Heads few-flowered and bracts few ; outer flowers pistillate. Somewhat 



woolly. 



Tribe V. HELIANTHEAE. Heads radiate or discoid. Involucre not scarious (nut-like in fruit in 

 nos. 40, 41, and 42). Receptacle chaffy. Pappus never capillary, sometimes none. Anthers 

 not caudate. Style-branches truncate or hairy-appendaged. 



* Ray-flowers fertile and ligulate (sometimes obscurely so); disk-flowers sterile. 



+- Achenes thickish, not strongly flattened either way. 



88. Polymnia. Achenes partially enveloped by the inner bracts of the involucre, these unarmed. 

 Perennials. 



84. Acanthospermum. Achenes closely invested by the glochidiate or prickly inner involucral 



bracts. Annuals, 

 i- - Achenes strongly flattened parallel to the bracts of the involucre, i.e. obcompressed. 



85. Silphium. Achenes wing-margined, in several rows ; pappus none or of 2 teeth. Bracts of 



tin- involucre thick, in several rows. 

 '56. Berlandiera. Achenes wingless, 5-12 in one row, without pappu>. Involucral bracts thin, 



oliovate, the outer smaller and more foliaccniis. 

 37. Chrysogonum Achenes wingless, about 5; pappus :i one-sided 2-3-toothed crown. Inner 



bracts :.. eliatV-likc, the outer 5 longer and leaf-like. 



88. Parthenium. Rays 5, very short, persistent. Pappus of 2 small chaffy scales. Involucral 



bracts short, roundish, in 2 rows. 



* * None ofth.- Howers ligulate, the fertile few (l-. r >). with minute tubular corolla or none. 



-i- Heads alike. 



89. Iva. Achenes -hurt, thick. Involucre of few roundish bracts. 



