1148 AMBROSIACEAE 



villous within. Stamens 5, free, epigynous : filaments distinct. Ovary inferior or nearly 

 so, 2-celled or rarely 1-celled : stigma surrounded by a ciliate indusium. Ovules 1 in each 

 cavity, or 2 in 1-celled ovaries, erect. Berry with a fleshy exocarp and a bony or woody 

 endocarp. 



1. Scaevola Plumiferi Vahl. Perennial, nearly glabrous, more or less shrubby. 

 Stem terete, low : leaves alternate ; blades obovate, 4-6 cm. long, entire, narrowed into 

 very short winged petioles, or nearly sessile, bearing a tuft of silky haiis in each axil : 

 peduncles shorter than the leaves : calyx-lobes much broader than high, rounded : corolla 

 glabrous without, about 2.5 cm. long ; tube shorter than the lobes, woolly within, split on 

 one side to the base ; lobes nearly linear, with broad crisped wings : stamens nearly as long 

 as the corolla-tube hanging through the cleft : berry oval, 10-14 mm. long. 



Coast of southern Florida and the Keys, also in the West Indies, South America, Africa and Asia. 



Order 14. CARDUALES. 



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

 toothed. Flowers perfect, monoecious or dioecious, few or many aggregated on 

 a receptacle and surrounded with an involucre of few or many bracts, or the in- 

 volucre rarely obsolete. Calyx 1 or 2 rows of bristles, scales, a mere border or 

 a crown, or obsolete or wholly wanting. Corolla of several more or less united 

 petals. Androecium of usually 5 stamens, the anthers merely converging, or 

 united. Gynoecium mostly of 2 united carpels. Ovary inferior. Styles or stig- 

 mas 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. AMBROSIACEAE. 



Stamens united by the anthers, thus forming a tube around the stigma, ex- 

 cept in Kuhnia. Fam. 2. CARDUACEAE. 

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



FAMILY 1. AMBROSIACEAE Reichb. RAGWEED FAMILY. 



Annual or perennial herbs or rarely shrubby plants, commonly weeds or 

 weed-like and either monoecious or dioecious. Leaves alternate, or opposite on 

 the lower part of the stem. Flowers very small, in inconspicuous heads, with 

 white or greenish disks, the staminate and pistillate in the same heads or in 

 separate heads. Involucres of few distinct or united bracts, those subtending the 

 pistillate flowers often longer than those of the staminate and usually nut-like or 

 bur-like at maturity. Staminate flowers with tubular obconic or funnelform 

 corollas ; lobes 4-5 : stamens usually 5, distinct : anthers merely converging, fur- 

 nished with in flexed appendages. Pistillate flowers without a corolla or this 

 represented by a mere border or short tube : calyx wanting or a mere border. 

 Ovary 1-celled. Stigmas 2, hairy or brush-like at the top. Achene naked or 

 enclosed in the accrescent pistillate involucre, which is commonly furnished 

 either with tubercles or spines. 



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. XANTHIUM. 



Bracts of the staminate involucres united. 



Pistillate involucres with numerous prickles in several rows. 2. GAERTNERIA. 



Pistillate involucres with several tubercles or prickles in 1 row. 3. AMBROSIA. 



Staminate and pistillate flowers in the same heads. 4. IVA. 



1. XANTHIUM L. 



Annual or perennial, commonly coarse herbs with upright or diffuse smooth or prickle- 

 armed stems. Leaves alternate : blades toothed or lobed, often ample. Heads monoecious : 

 staminate in terminal spikes, racemes or clusters : pistillate axillary. Staminate involu- 

 cres short, of several distinct bracts, in 1-3 rows. Receptacle chaffy, cylindric. Corolla 

 tubular : lobes 5. Filaments monadelphous. Anthers mucronate, free. Style simple. 

 Pistillate involucres closed, 1-3-beaked, oblong to ovoid, armed with spines, 2-celled. 

 Corolla wanting. Stigmas 2. Achenes solitary in each cavity of the involucre. Pappus 

 wanting. The plants bloom in summer and fall. CLOTBUR. BURWEED. COCKLEBUR. 



