StNGENESIA. NECESSARIA, 183 



596. SILPHIUM. L, 



Calix squarrose, scales broad and foliaceous. 

 Receptacle paleaceous. Seed flat, obcordate, 

 emarginate, bideiitate. 



Herbaceous, often tall; stem cylindric or ang-ular; leaves 

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

 tifid; flr>vvers tastig'iate, axilkr ami terminal, yellow. — 

 Hermaplirodite and sterile tliscal fiores producmg' as in 

 Alciiia a simple subclavate style; dentures small and pu- 

 bescent. Seeds margmated. 



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

 thinacenm. 4. perfoliatum. 5. connatum. 6. AsteriscuHy 

 6. * scabrurn. Leaves opposite or alternate, oblon^-lanceo. 

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

 liate. 7. pumilum, /3. tomentosum. S. toinentosum, Ph. 

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

 side canescently villous; stem subtomentose; calix spread- 

 ing"; seeds naked. 8. integrifrjlium 9. liCvigatum. Ph. 

 10. trifoUaium. 11. iernatnm. 12. atropurpureum. A va- 

 riety of the preceding. 13. elatum. Herb. Banks, mss. 

 Not defined. 14. reticulatumt ibid. Destitute of cliaracter. 



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 yellow. 



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

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



A North American genus, with the exception of a third 

 species in Abyssinia. 



598. PARTHENIUM. Z. 



Calix 5-leaved. Raijs very small. Receptacle 

 paleaceous, minute; exterior scales dilated. Seed 

 obovate, minutely 3-a\vned. 



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- 



