130 



FIELD COLUMBIAN MUSEUM BOTANY,, VOL. III. 



heads, sessile or nearly so in the axils or terminal on the branches. 

 Heads 9-12 mm. high, 5 mm. broad, about 15 flowered. Involucral 

 bracts in 2 series, at first erect, 

 more or less spreading at ma- 

 turity, oblong-lanceolate, sub- 

 acute, striate, the outer pair 

 little longer, foliaceous and pu- 

 bescent toward the summit, inner 

 glabrous. Corollas yellow; rays 

 inconspicuous, ligule 1.5 mm., 

 bidentate, erect. Receptacle con- 

 oid; scales oblong-lanceolate, 

 obtuse, erose-denticulate at the 

 summit. Ray achenes slate color 

 with stramineous wings; includ- 

 ing wings but not awns 2x3.8 

 mm.; oblong-obovate; in sec- 

 tion convexo-concave; smooth, 

 the lacerate wings becoming 

 corky-turgid and awned at ma- 

 turity; apical awns stout, hispidulous, i mm. long; disk achenes brown, 

 1x3.8 mm., oblong-cuneate ; in section subplano convex; covered 

 with irregular, longitudinally elongated tubercles, hispidulous; awns 

 2 or 3, hispidulous, the middle 1-3 mm. long or wanting, lateral 4-5 

 mm. long. 



Hab. Merida, at the Quinta del Obispo, Nov. 15, 1864, Schott 

 93 (Synedrella nodiflora Gaertn. Field Col. Mus. Bot. 1:397); campo 

 about Izamal, Jan. 23, 1895, Millspaugh Armour Exped. 183 Synedrella 

 nodiflora Gaertn. Ibid. 1:54); "herb 6-18 inches high, common in waste 

 places near Izamal, in bloom throughout the year," Gaumer Jjp, 952 

 (Synedrella nodiflora Gaertn. Ibid. 1 1397) Calotmul 1694, Chichankanab 

 2085, San Anselmo 2086. 



BIDENS L. Sp. PI., 831. 



Heads heterogamous, radiate; ray flowers neutral, ligulate; disk 

 flowers perfect, fertile, tubular. Involucre campanulate or subhemi- 

 spheric, of narrow bracts imbricated in 2-3 series, outer herbaceous, 

 connate at base, inner membranaceous. Receptacle plane or convex, 

 chaffy; scales narrow, plane, subtending the disk flowers. Achenes 

 dorsally compressed, somewhat 4 angled, linear-oblong in our species; 

 pappus of 2-4 rigid persistent awns. Annual or perennial herbs, or 

 slender shrubs. 



Awns 2: 



Achenes spinulose 



Achenes hirsute on the margins 

 Awns 4 



leitcantha. 



tereticaulis. 



bipinnata. 



Bidens leucantha (L.) Willd. Sp. PL, 3:1719. 

 Coreopsis leucantha L. 



Bidens pilosa L. Sp. PI. 832 the discoid form? 

 An erect, simple or branching annual with 4-sided striate, glabrate 



