SYNANTHEREJ!. 369 



formity with the allied genera Pinilloda and Microcoecia) : hence Ogiera would he much 

 more distant, haying palea: at all flowers, and shortly-tailed anthers. 



84. O. ruderalis, Gr. — Melampodium, Sw. KegeKa, Schultz. Sip. I Tetranthus, PI. 

 Carib. O. triplinervis, a leiocarpa, Cass. — Variable in down, and in the achenia tubercled or 

 smooth. Leaves ovate, hluntish, shortly petioled ; palese scariose, ciliate above, acnpiinate, 

 exceeded by the 5-leaved involucre. — Hab. Jamaica!, Al., a weed; Trinidad!, Sch., Cr.i 

 [Cuba 1, Virgin and French islands ! ; Venezuela 1, Guiana I, Brazil !]. 



22. ACANTHOSPERMUM, Schri. 



Head heterogamous, 10-20-flowered : exterior flowers ? , minutely ligulate, interior $ 

 tubular. Involucre foliaceous, 1-serial. Receptacle paleaceous: exterior paleee bearing 

 uncinate prickles, including the achenia. Column becoming blackish, including a simple, 

 pubescent style. — Jchenium compressed, naked. — Difinse, annual herbs; leaves opposite, 

 glandular beneath ; heads subsessile, terminal, often between dichotomous branches, yellow, 



85. A. humile, DC. Pubescent ; leaves lyrate or obovate, subsessile at the tapering 

 base, unequally dentate ; ? flowers 5-4 ; paleee cuneiform around the achenium, devoid 

 of grooves, viith 2 diverging beahs at the angles of the truncate top. — Melampodium, Sw, 

 — Hab. Jamaica I, all coll., a weed ; [Cuba !, Haiti ; Panama!]. 



, 86. A. xanthioides, DO. Pubescent; leaves obovate, petioled, denticulate (or sub- 

 entire) ; ? flowers 5 ; palets oblong around the achenium, sulcate, blunt at the unarmed 

 top. — Centrospermum, Eth. Melampodium australe, L. A. hirsutum, DC. Siegesbeckia 

 flosculosa, Sieb. Mart. 204 {non L'JSer.) : a glabrescent form. — Hab. Caribbean Islands, a 

 weed ; [Swedish and French islands ! ; Venezuela, Guiana I to Buenos Ayres !]. 



23. ENHYDRA, Lour. 



Bead discoid, heterogamous : exterior flowers ? , pluriserid, inferior S ■ Involucre folia- 

 ceous, 4-leaved : 2 leaves interior. Receptacle paleaceous : palese including each achenium 

 in pairs, sulcate-striate. Column becoming blackish. Style 2-fid : branches with an hispidu- 

 lous appendage. Achenium compressed-spathulate, naked: corolla-tube jointed with the 

 limb, subpersistent ; sterile achenia in S flowers slender, trigonal. — Aquatic herbs, ascend- 

 ing from a radicant base ; leaves opposite, glandular beneath ; heads solitary, aaAllary or 



87. E. sessilis, DC- Glabrescent or scabrous ; leaves sessile, oblong or ovate, pointed, 

 rounded at the base, remotely serrate ; heads sessile. — Meyera, Sw. — The South American 

 forms, which I compare, are little distinct — Hab. Jamaica I, Wullschl. ; [Haiti to Brazil I]. 



24. PARTHENIUM, i. 



Head heterogamous : 5 exterior flowers ? , minutely and broadly ligulate, interior nume- 

 rous, S . Involucre 2-serial. Receptacle paleaceous : palete dikted above, geminate at 

 the achenia. Anthers pale: style simple, pubescent. Achenium compressed: pappus of 

 2 scales or obsolete. — ^Annual or suffiutescent herbs ; leaves alternate ; heads in corymbs fir 

 panicles, whitish. 

 1^ 88. P." Hystefophonis, Z. Annual, tall, hispidulous; leaves 2-pinnatipartite, the up- ^ 

 permost entire ; heads in spreading panicles ; pappus-scales oblong, blunt. — Heads \\"'-%"' Q 

 diam. — Hab. Bahamas !, Swains. ; Jamaica !, Macf., Fd., a weed ; S. Kitts !, Sis., Anti- 

 gua!; Wullschl., Dominical, Imr., S. Vincent!, Guild.; Trinidad!; [Cuba! and Louisiana ! 

 to Northern Patagonia! and Mendoza I]. 



25. AMBROSIA, i. 



Heads monoecious, homogamous, superior 3 , inferior ? . 3 ■■ Involucre of united scales. 

 Receptacle paleaceous, rarely naked : palese linear. Anthers distinct, pale : connective with 

 a terminal, inflexed bristle. Style simple, peniciUate at the top. ? : Involucre closed, 

 l-flowered : flower naked. Achenium ovoid, naked.— Annual or sufirutescent herbs ; leavca 



