432 AMBKOSIACEAE. 



funnelform, 5-tootlied; anthers scarcely coherent, mucronate-tipped; style un- 

 divided, penieillate at the summit. [The ancient classical name.] About 15 

 species, mostly natives of America. Type species: Ambrosia maritima L. 



Annual ; erect ; pubescent or puberuLent. 1. A. paniculata. 



Perennial ; repent ; hirsute or hispid. 2. A. hispida. 



1. Ambrosia paniculata Michx. Fl. Bor. Am. 2: 183. 1803. 



Annual, pubescent or puberulent, paniculately branched., 3-12 dm. high. 

 Leaves thin, 1-2-pinnatifid, petioled, 5-8 cm. long, the upper alternate, the 

 lower mostly opposite, pale or canescent beneath, the lobes oblong or lanceo- 

 late, obtuse or acute; racemes of sterile heads numerous, 212 cm. long, the 

 involucres hemispheric, about 3 mm. broad, crenate; fertile heads few, obovoid 

 or subglobose, 2-3 mm. long, short-beaked, pubescent. 



Waste places at Nassau, New Providence : Florida ; Cuba ; Hispaniola ; Jamaica ; 

 continental tropical America. Referred by Dolley and by Hitchcock to A. artemisiae- 

 folia L. SOUTHERN RAGWEED. 



2. Ambrosia hispida Pursh, Fl. Am. Sept. 743. 1814. 



Ambrosia crithmifolia DC. Prodr. 5: 525. 1836. 



Perennial, hirsute or hispid; stems branched at the base, the branches 

 diffusely spreading or ascending, 2-8 dm. long, leafy. Leaves opposite, 2-3- 

 pinnately divided, rather firm in texture, 4-12 cm. long, short -petioled ; racemes 

 of sterile heads elongated, mostly solitary, the involucres spiny-pubescent; 

 fertile heads clustered., 2.5-3 mm. long, short-beaked, usually tubercled. 



Sea-beaches, throughout the archipelago: Florida; Cuba; Hispaniola; Porto 

 Rico ; Virgin Gorda to Barbadoes ; Mexico. S'WEET-BAY. BAY GERANIUM. BAY TANSY. 



3. IVA L. Sp. PI. 988. 1753. 



Puberulent or scabrous herbs or shrubs, with thick opposite leaves, or the 

 upper alternate, and small nodding, axillary and solitary, spicate racemose or 

 paniculate heads of greenish flowers. Involucre hemispheric or cup-shaped, its 

 bracts few, rounded. Eeceptacle chaffy, the linear or spatulate chaff envelop- 

 ing the flowers. Marginal flowers 1-6, pistillate, fertile, their corollas short, 

 tubular or none. Disk-flowers perfect, sterile., their corollas funnelform, 5- 

 lobed, their styles undivided, dilated at the apex. Anthers entire at the base, 

 yellow, scarcely coherent with each other, tipped with mucronate appendages. 

 Achenes compressed, obovoid, glabrous. Pappus none. [Named after Ajuga 

 Iva, from its similar odor.] About 12 species, natives of America. Type 

 species: Iva annua L. 



Involucres about 5 mm. broad ; plant glabrous ; leaves mostly 



alternate. 1. /. irtibricata. 



Involucres 3-4 mm. broad ; plant pubescent ; leaves opposite. 2. I. cheiranthifolia. 



1. Iva imbricata Walt. Fl. Car. 232, 1788. 



Perennial by woody roots, glabrous or nearly so throughout, fleshy; stem 

 3-6 dm. high, simple, or sparingly branched. Leaves all but the lowest alter- 

 nate, sessile, oblong-spatulate, or lanceolate, obtusish, mucronulate, entire, or 

 rarely serrate, obscurely 3-nerved, the larger 3-5 cm. long, 6-10 mm. wide; 

 heads short peduncled or nearly sessile, the upper ones longer than their sub- 

 tending leaves; involucre broadly campanulate, about 5 mm. broad, its bracts 

 6-9, somewhat imbricated in 2 series; fertile flowers 2-4, their corollas tubular, 

 the staminate ones much more numerous. 



Sea-strands, Great Bahama, Great Harbor Cay, Andros, New Providence and 

 Inagua : Virginia to Florida and Louisiana ; Cays of northern Cuba. BEACH IVA. 



