Calendula. LXXV. COxMPOSIT^. 353 



59. AMBROSIA. 



Gi". afilSpoaia, food of the gods ; a terra .strangely applied. 



Heads heterocephalous. Sterile. — Involucre of several united 

 scales, hemispherical, many-flowered ; anthers approximate, but dis- 

 tinct ; receptacle naked. Fertile. — Involucre 1 -leaved, entire or 5- 

 toothed, J -flowered, corolla ; styles 2 ; stamens 0. — Herbaceous 

 flants with mostly opposite Ivs. arid unsightly Jloioers. 



1. A. TRiFiDA. Tall Avibr<.sia. 



Hairy, rongh ; Ivs. three-lobed, serrate, the lobes oval-lanceolote, acumi- 

 nate ; //-. with 6 lines below the summit. — (J) A very tall, herbaceous plant, not 

 very common in N. Eng., found in hedges and low grounds in the valley of 

 Connecticut river. In fhe W. States it is abundant! Stem 5 — lOf high, erect, 

 branching, furrowed. Leaves opposite, in 3 large, deep lobes with long points 

 and close serratures. Flowers mean and obscure, in long, leafless spikes, axil- 

 lary and terminal. Aug. 



0. inlegrifolia. T. & G. (A. integrifolia. Muhl.) Lvs. ovate, acuminate, 

 serrate, bristly on both sides, ciliate at base, often some of them 3-lobed ; rac. 

 terminal, single or ternate. 



2. A. ARTEMisiiEFOLiA. (A. clatior. Ph.) Hog-ioeed. 



Lvs. twice-pinnatifid, nearly smooth; petioles ciliate; rac. terminal, pani- 

 cled; 5<. virgate. — (p A common and troublesome weed of the gardens, fields, 

 &c. (Can. to Ga.) far more worthy of its English than its Latin name. Stem 

 2 — 3f high, branching, pubescent when young. Leaves with segments acute 

 and parallel. Barren flowers, small, green,* in terminal racemes, the fertile 

 ones sessile about the axils of the upper leaves. Aug. Sept. 



3. coRONOPiFOLiA. Torr. & Gray. 



Canescent-strigose, branched ; lvs. crowded, rigid, the lower opposite, bi« 

 pinnatifid, upper lanceolate, sessile, pinnatifid ; sterile hds. spicate,_/e?//fe clus- 

 tered at the base of the sterile spikes, in the axils of the upper leaves; fr. hairy. 

 — ® Prairies, Wis. to Tex. Stem 1 — of high, at length ver}' branching and 

 leafy. Aug. Sept. 



4. A. BIDENTATA. MichX. 



Very hirsute; st. branching; branches sinrple ; lvs. crowded, mostly alter* 

 nate, closely sessile or partly clasping, undivided, oblong, with a single tooth 

 or short lobe on each side near the base; sterile hds. den.sely spicate,/e/7ife axil- 

 lary ; fr. 4-angled, acutely pointed, the 4 ribs produced in 4 short spines. ® 

 Prairies, 111. to La. Stem 1 — 3f high, with numerous leaves and very dense, 

 terminal spikes. Jl. — Sept. 



GO. I V A . 



A name of barbarous origin. 



Heads discoid ; involucre o-leaved ; marginal flowers 5, fertile, the 

 others sterile ; receptacle hairy ; achenia obconic, obtuse ; pappus 0. 

 — Herbs or shrubs. Lower lvs. opposite. 



I. FRUTESCEN3. HigJi-watcr Shrub. Marsh Elder. 

 . St. shrubby; li's. lanceolate, punctate, deeply serrate, rough. — % In the 

 borders of salt marshes, Mass. to La., common. Stem thick, 3 — 8f high, with 

 numerous opposite branches. Leaves numerous, 3-veined, upper ones entire. 

 Flowers green, small, drooping, in close, leafy clusters. Aug. 



Tribe 5. CYNARE J3. 

 Heads ovoid, discoia, rarely radiate, homogamous (rareiy aitEcious), or hete- 

 rogamous with the marginal flowers in a single series. Style in the perfect 

 flowers often tumid near the summit. 



GL CALENDtJLA. 



Lat. calenda, the first day of the month ; some species blossom monthly. 



Heads radiate j involucre of many equal leaves, in about 2 series j 



