476 



SYNGENESIA NECESSARIA. 



u^ 



AMBROSIA. Gen. Pl. 



Monoica. 



Floris 



masculi — involucrum 1 

 phyllum, haemispheri- 



cum, 

 th erce 



Monoecious. 



Male 



fiorets 



involucrum 1- 



leaved, hemisphaerical, 



multiflorum; an- many flowered 



5 



an- 



approximatae 

 non coalitae; receptacu- 

 lum nudum. Flor. 

 foe m. — itwolucrum 

 pliyllum, sub 



1 



integer 



aut 5 dentatum; 1-flo 



corolla 

 styli 2; nux e 



5 



r u m ; 



indurato, 1-sperma 



nulla 



calyce 



? 



therms approximate not 

 united; receptacle nak- 

 ed. Female Jlorets — 

 involucrum 1-leaved, 

 entire or 5-tootlied, 1- 

 flowered 



styles 2 





coro lla 

 nut formed 



from the indurated ca- 

 lyx, 1-seeded. 



1. Trifida. 

 A. hirsuta 



Liii. 



} aspera; 

 foliis 3-Iobis, serratis, 



Hirsute 



? 



rough. 



lobis ovali-Ianceolatis, 

 acuminatis; fructu in- i latc, at^i 

 fra apicem 6-spinoso. | 6-spined 



summit. 



leaves 3-lobed, serrate, 

 the lobes oval-lanceo- 

 late, acuminate; fruit 



below 



the 



Sp. pl. 4. p. 3r5. Mich. 2. p. 183. Pursh, 2. p. 581. Nutt. 2. p. 186. 



Flant annual, four to eight feet high. Stem hairy, and scabrous. Leaves 

 generally opposite, rather large, deeply three-cleft, hairy and scabrous, the 

 segments lanceolate, acuminate, serrate. The flowers as in all of this genus 

 maybe considered as in large terminal panicles composed of axillary and 

 terminal spikes. The heads of male florets numerous, solitary, somewhat 

 crowded along the summit of the spike; the fertile florets in small clusters of 

 two to five at the base, surrounded by two or three bracteal leaves. Involu- 

 crum of the male florets one-leaved, five to eight lobed, hairy. Corolla 

 small, tubular, white. Stamens distinct. Involucrum of the fertile florets 

 five-lobed, persistent, germ somewhat obovate, abruptly acuminate. Styles 

 two, distinct. JN'ut one-celled, one-seeded, formed of the indurated involu- 

 crum, crowned with six short spines or teeth surrounding the acuminated 

 summit. 



