144 AMBROSIACEAE. 



woolly within; lobes linear to lanceolate: berries oval to globular, 10-14 mm. 

 long, black. Coastal sand-dunes and hammocks, U. S. keys, U. keys. L. keys, 

 L. S. keys. [E. K.] (Ber., Bah., Cuba, Ant.) 



Order CARDUALES. 



Herbs, shrubs, or rarely trees. Leaves mainly alternate : blades entire, 

 toothed, or divided. Flowers perfect, monoecious, or dioecious, few or 

 many aggregated on a receptacle and surrounded with an involucre, or 

 the involucre rarely obsolete. Calyx one or two rows of bristles, scales, a 

 mere border or crown, or obsolete, or wanting. Corolla of several more 

 or less united petals, or wanting. Androecium of usually 5 stamens, the 

 anthers converging, or united. Gynoecium mostly of 2 united carpels. 

 Ovary inferior. Styles or stigmas mostly 2. Fruit an achene. 



Flowers with tubular corollas, or those of the outer ones prolonged into ligules. 

 Stamens distinct, the anthers merely converging about the stigma. 



Fam. 1. AJIBROSIACEAE. 

 Stamens united by the anthers, thus forming a tube 



around the stigma, except in Kuhnia. Fam. 2. CARDUACEAE. 



Flowers with each corolla prolonged into a ligule. Fam. 3. CICHOBIACEAB. 



FAMILY 1. AMBROSIACEAE. RAGWEED FAMILY. 



Annual or perennial, weedy 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. 



Staminate and pistillate flowers in different heads : involucre of the pistillate head 



bur-like or nut-like. 

 Bracts of the staminate involucres distinct : pistillate involucres bur-like. 



1. XAXTHIUM. 



Bracts of the staminate involucres united. 2. AMBROSIA. 



Staminate and pistillate flowers in the same heads. 3. IVA. 



1. XANTHIUM L. Coarse, sometimes spiny herbs. Leaf-blades large, 

 toothed or lobed. Mature pistillate involucre copiously and evenly spiny. 



1. X. americanum Walt. Plants glabrate or finely pubescent, 2-13 dm. 

 tall: leaf -blades ovate or deltoid, 5-30 cm. long, rather coarsely toothed and 

 more or less distinctly lobed: fruits oblong, 15-20 mm. long, thickly beset with 

 slender, more or less hooked spines. Cultivated grounds and waste places, 

 Key West. CLOTBUR. BURWEED. COCKLEBUR. 



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

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



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



1. A. elatior. 

 Leaf -segments numerous : stem decumbent or prostrate : staminate 



corollas 2 mm. long or more. 2. A. hispida. 



1. A, elatior L. Annual, mostly 3-6 dm. tall, 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-pubescent :" achenes 2-2.5 

 mm. long, the tubercles at or near the top. [A. artemisiifolia L.] Pinelands 

 and coastal sand-dunes, U. S. keys, U. keys, L. keys. [E. K.] (Ber., Bah.) 



