COMPOSITE FAMILY. 



169 



Receptacle nakeJ. 



Pappus of siendor but rather stiff bristles. Flowers 



■whitisli or purplisb. Scales of involucre several. 2. EuPATORira 



Pappus of very soft and weak naked bristles. Flowers 



yellow. *22. SEXEao. 



** Flowers of two kinds in the same heads. 

 Marginal flowers neutral and sterile, commonly enlarged. 23. Centaurea, 



Marginal flowers pistillate and fertile. 



Receptacle naked or bearing no conspicuous chaff. 



Pappus of capillary bristles. Scales of the involucre imbri- 

 cated, dry and scarious. 20. G-VAPH-iiir3i. 

 Pappus of capillary bristles. Involucre of but one row of 

 scales. 



Heads very small. *o. Erigerox. 



Heads large. Pappus copious, very white. 21 Erechthites. 



Pappus obsolete or none. 



Akenes broad at the top. Pappus a short crown. IS. TAXACErrir. 



Akenes narrow at the top. Pappus none. 19. AiHEinsiA. 



«=** Flowers of two kinds in separate heads ; one pistillate, the other 



staminate. 

 Heads moacEcious. 



Fertile involucre small, 1-flowered, poicied and often tubercled. 8. Ambrosia. 

 Fertile involucre an oblong prickly bur, 2-celled, 2-seeded. 9. XA>THn:>i. 



§ 2. Kays present ; i. e., the marginal flowers, or some of them, 

 with strap-shaped (ligulate) corollas. 



* Pappus of capillary bristles. (Rays all pistillate.) 

 Rays occupying several rows. 



Heads solitary upon a scape. 3. Tusstlago. 



Heads more or less corymbed. **5. Erigerox. 



Rays in one marginal row, and 



White, purple or blue, never yeUow. Pappus simple. 4. Aster. 



Yellow, of the same color as the disk. 



Scales of the involucre in one row. Pappus soft and weak. **22. SExeao, 

 Scales of the involucre imbricated. Pappus simple. 



Heads small, racemed or clustered. & Soltdago. 



Heads Large,' terminating the branches, 7. Ixcla. 



** Pappus none, or a cup or crown, or 2 - 3 a-wns, teeth or chaffy scales 

 corresponding with the angles or edges of the akene, often with inter- 

 vening minute bristles or scales. 



J Receptacle naked. 



Akenes terete or angled. Pappus none. Receptacle flattish. 17. LEtrcAXTHEirrs 



ff Receptacle chaffy. 

 Rays neutral (rarely pistillate but sterile) ; the disk flowers perfect. 

 Receptacle strongly convex or columnar, and 



Chaffy only at the summit ; the chaff deciduous. 



Pappus none. 14. SlARtrrA. 



Chaffy throughout. 



Akenes 4-sided, flat at the top. Pappus none, or a minute 



crown. 10. Rudbeckia. 



Akenes flattened laterally. Pappus of 2 deciduous scales. 11. Heuaxthus 

 Akenes flat, wing-margined, bearing 2 persistent awns. 12. AcnxoMERia 

 Receptacle flat. 



Akenes flat or 4-sided, with 2 or more downwardly barbed 

 persistent awns. 13. Bidexs. 



Rays pistillate and fertile, as well as the disk flowers. 



Akenes flattened and margined. Pappus none. 16. AcmujEA. 



Akenes 4-angled or terete. Receptacle convex or conical. Leaves 

 alternate, dissected. 15. Axthehk, 



SUB-OEDER 2. LlGULIFLOE^. 



Corolla ligulate in all the flowers of the head, and all the flowers per- 

 fect. Herbs with milky juice and alternate leaves. 

 Pappus of numerous small chaffy scales. 



Flowers blue. 28. CiCHORim. 



