182 AMBROSIACEAE. 



Flowers with tubular corollas, or those cf the outer ones prolonged Into llgules. 

 Stamens distinct, the anthers merely converging about the stigma. 



Fam. 1. AMBROSIACEAE. 

 Stamens united by the anthers, thus forming a tube 



around the stlgmn, except In Kuhnia. Fam. 2. CABDUACEAE. 



Flowers with each corolla prolonged Into a llgule. Fam. 3. CICHORIACEAB. 



FAMILY 1. AMBROSIACEAE. RAGWEED FAMILY. 



Annual or perennial, woody herbs, the plants often coarse. Leaf- 

 blades entire, toothed, lobed, or divided. Flowers in inconspicuous heads, 

 the bracts of the pistillate heads distinct or sometimes united and accres- 

 cent into a bur. Fruit-producing flowers apetalous or with much reduced 

 corollas. Achenes subtended by or enclosed in an involucre. Pappus 

 wanting or obsolete. 



Stamlnate nnd pistillate flowers In different heads: achenes spiny or tubercled. 



1. AMBROSIA. 

 Stamlnate and pistillate flowers In the same heads : achenes smooth. 2. IVA. 



1. AMBROSIA [Tourn.] L. Leaf-blades toothed, lobed, or divided. 

 Mature pistillate involucre tuberculate or spiny near the top. RAGWEED. 



Leaf-segments few : stems erect : Stamlnate corollas less than 2 mm. long. 



1. A. clatior. 



Leaf-segments numerous : stem decumbent or prostrate : Staml- 

 nate corollas 2 mm. long or more. -. i. /ii/,i./.i. 



1. A. elatior L. Annual, mostly 3-6 dm. tall or diffuse, the stem and 

 branches sparingly pubescent: leaf-blades sparingly pubescent, the ultimate 

 segments lanceolate to linear-lanceolate, acute or acuminate : peduncles slender, 

 mostly shorter than the involucres: staminate involucres sparingly fine-pubes- 

 cent: achenes 2-2.5 mm. long, the tubercles at or near the top. [A. artitm-si- 

 folia, L.] Pinelands and coastal sand-dunes. F. K. (Ber., Bah., Cuba, Ant.) 



2. A. hispida Pursh. Perennial, the stem and branches decumbent or pr. 



the younger parts hirsute: leaf-blades short-hirsute, the ultimate segments 

 smali, short and rounded: peduncles stout, minutely hirsute: staminate invo- 

 lucres finely hirsute: achenes 4-4.5 mm. long. Coastal sand-dunes. F. K. 

 (Bah., Cuba, Ant.) 



2. IVA L. Leaf -blades entire or toothed. Mature pistillate involucre not 

 bur-like. MARSH-ELDER. 



Involucres peduncled ; bracts suborblcular or renlform : stnmlnate corollas 2.5-4.5 



mm. long : achenes 2-3.fi mm. long. 



Leaf-blades entire or nearly so: Involucres of 0-0 bracts. 1. /. io\bri<;itn 

 l.i-af blades coarsely serrate: Involucres of 4 or 5 bracts. 2. /. (int. 

 Involucres senile; bracts obovate : staminate corollas 1.5-2 

 mm. long: achenes about 1.5 mm. long. .".. /. mi. <i>hala. 



1. I. imbricaU Walt. Stems 3-7 dm. long, smooth and glabrous: leaf -blades 

 linear-subulate to linear, 2-5 cm. long, glabrous: involucre 3-4 mm. high: 

 achenes about 3-3.5 mm. long. Coastal sand-dunes and rocky shores. F. K. 

 (Bah., Cuba.) 



2. I. frutescens L. Stems 8-35 dm. tall, pubescent or puberulent : leaf -blades 

 elliptic, oblong-lanceolate, or oblong-linear, 5-10 cm. long, coarsely serrate: 

 involucres 3.5-4 mm. high; bracts 2-3 mm. long: achenes 2-2.5 mm. long. 

 Salt marshes. 



3. I. mlcrocephala Nutt. Stems 3-9 dm. tall, glabrous or nearly so: leaf- 

 blades narrowly linear, 2-5 cm. long, entire or slightly toothed: involucres 

 campanulate, 2 mm. high, each with 3 fructiferous flowers: corolla nearly 2 

 mm. long: achenes about 1.5 mm. long. Everglades. 



