SYNANTHERE2E. 369 



formity with the allied genera Pinillosia and Microcoecia) u hence Ogiera would he much 

 more distant, having paleae at all flowers, and shortly-tailed anthers. 



84. O. ruderalis, Gr. — Melampodium, Sw. Kegelia, Schultz. Bip. ! Tetranthus, PI. 

 Carib. 0. triplinervis, a leioearpa, Cass. — Variable in down, and in the achenia tubercled or 

 smooth. Leaves ovate, bluntish, shortly petioled ; palese scariose, ciliate above, acuminate, 

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

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



22. ACANTHOSPERMUM, Schrk. 



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

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

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

 pubescent style. — Achenium compressed, naked. — Diffuse, 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, with 2 diverging beaks at the angles of the truncate top. — Melampodium, Sw. 

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



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

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

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

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

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



23. ENHYDRA, Lour. 



Head discoid, heterogamous : exterior flowers ? , pluriserial, interior $ . Involucre folia- 

 ceous, 4-leaved : 2 leaves interior. Receptacle paleaceous : palea 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 $ flowers slender, trigonal. — Aquatic herbs, ascend- 

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

 terminal. 



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 !, Wullschl. ; [Haiti to Brazil !]. 



24. PARTHENIUM, L. 



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

 rous, $ . Involucre 2-serial. Receptacle paleaceous : paleee dilated above, geminate at 

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

 2 scales or obsolete. — Annual or suffrutescent herbs ; leaves alternate ; heads in corymbs or 

 panicles, whitish. 



88 P. Hysteroplioms, !•■ Annual, tall, hispidulons ; leaves 2-pinnatipartite, the up- 

 permost entire; heads in spreading panicles; pappus-scales oblong, blunt. — Heads \\ m -2! n 

 diam. Hab. Bahamas!, Swains.; Jamaica!, Macf., Pd., a weed; S. Kitts!, Els., Anti- 

 gua! Wullschl., Dominica!, lmr., S. Vincent!, Guild. ; Trinidad!; [Cuba! and Louisiana! 

 to Northern Patagonia! and Mendoza !]. 



25. AMBROSIA, L. 



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

 Receptacle paleaceous, rarely naked: paleee l.near Anthers durtmct, pale : ^connect.ve iwith 

 a terainal,infJexed bristle. Style s>mple , pemcdlate at the top? , Involucre closed, 

 I flowered • flower naked. Achenium ovoid, naked.— Annual or sufirutescent herbs ; leaves 



