SYNGENESIA. NECESSARIA. 183 



096. SILPHIUM. Z. 



Calix sqiiarrose, scales broad and foliaceous. 

 Receptacle paleaceous. Seed flat, obcordate, 

 emargiiiate, bidentate. 



Herbaceous, often tall; stem cylindricor ang-ular; leaves 

 alternate, opposite, or rarely verticillate, entire or pinna- 

 ( lificl; flowers fastig"iaie, axillar and terminal, yellow.- 

 Hermaphrodite and sterile discal ftorels prodiAcing ai 

 Akina a simple subclavate style; dentures small and 

 bescent. Seeds marg-inated. 



Species. 1. S. laciniatum. 2. compoaitnm, 3. terebin- 

 thinaceiim. 4. perfoliutum. 5. coitnation. 6. Asteriscus, 

 ^. * scabrum. Leaves opposite or alternate, oblong-lanceo. 

 late, aubcrenate, acute, sessile and scabrous; calix subci- 

 liate. 7- pumilnm, /3. tomentosnm. S. tomentosunif Ph. 

 Leaves alternate, cordate-ovate, crenate, obtuse, under 

 side canescendy villous; stem subtomentose; calix spread- 

 ing; seeds naked. 8. inte^rifoham. 9. Uvigatum. Ph. 

 10. trifoiiiUitm. 11. ternatum. 12. afrop/D^pureum. A va- 

 riety of the preceding. 13. e^atum. Herb. Banks, mss. 

 Not defined. 14. reticulatumy ibid, iicsiitute of character. 



A North American genus. 



597. POLYMNIA- L. 



Calix double; exterior 4 or 5-leaved ; interior 

 10-leaved, leaflets concave. Receptacle paleace- 

 ous. Pappus none. 



Herbaceous; stems tall; leaves opposite and alternate, 

 mostly lobed or subpinnatifid ; flowers terminal, rays 

 small, pale } ellow. 



Species. 1. P. canadensis. 2. Uvedalia. Stem very 

 tall. Seeds large. Styles of tlie discal florets partly bifid. 



A North American genu^, with the exception of a third 

 species in Abyssinia. 



598. PARTHENIUM. Z. 



Calix 5-leaved. Rays very small. Receptacle 

 paleaceous, njinute; exterior scales dilated. Seed 

 obovate, minutely 3-awned. 



Herbaceous; leaves alternate, simple or pinnatifid; flow- 

 ers corymbose, terminal. — The 5 external scales of the 

 receptacle very broad, shielding the same number of mi- 



ives 



ina- m 



