I'll Ci'Ml'oslT.K. (COMl'dSlTK rAMILV.) 



0- Ii' itiiwcrod ; scales of tin- invohicro 4 - 5, rjliovate, ciliate; fertile flowers 

 1 -.3, — Dry l.arreii soil, Florida to Soiitli Carolina. >\u<^nst - S('j)t. — Stem 

 l°-2M.i.-jli. 



3. I. ciliata, Wiiid. Anmial, liisjiid ; stem l)rarKliiiig; leaves ovate, 

 acuminate, ooarsidy si-rrate ; spikes dense, the bracts elongated ; .scales of the 

 involture .'J -4, nmndisli, ciliate; fertile flowers mostly 3. — Mississi]i|ji 

 iCdijiriilci), and westward. Sept. — Stem 2"^ -3° high. Leaves 3' -4' long. 



* * Srdlts (if' till' iiiniliirri- (5-9, liiilin'riilcd in 2-4 roics. 



4. I. imbricata, Walt. Somewiiat shruliby, smooth ; leave.-? fleshy, 

 lanceolate, the lower ones slightly serrate and 3-ril)l)ed, the upper alternate 

 and entire; hea<ls many-tiowered ; outer scales of tlie involucre orbicular; 

 the inner olxnate, toothed margined ; fertile Howers 2-4, the short corolla 

 .'j-parted. — \'aries with smaller and fewer-flowered heads, and the corolla of 

 the fertile flower truncate. — Drifting .sands along the coa.'it, Floriila to North 

 Carolina. August-Sept. — Stem 1^-2^ high. Leaves 1' long. 



42. AMBROSIA, Tourn. 



Heads monfrcious, in racemes or spikes; the uj)per ones sterile, nod<ling; 

 the lower ])istillate and fertile. Involucre of the sterile flowers composed of 

 7-12 united .scales, 5 - 20-flo\vered. Keceptaele naked or with slender chaff. 

 Corolla 5-toothed. Involucre of the fertile flowers 1 -flowered, ovoid or turbi- 

 nate, entire, closed, pointed, commonly with a row of tubercles or spines near 

 the apex. Corolla and stamens none. Acheuia globose or ovoid. Paj)])us 

 none. — Herbs. Leaves mostly pinnately lobed. Fertile flowers single or 

 clustered at the base of the sterile spike, or in the axils of the upper leaves, 

 bracted. Flowers whitish. 



♦ Heads of sterile flowers denselij spiked, the top-shaped involucre produced on 

 one side into a lonij recurved ajipenduge : fertile heads axillary, 4--fin(/led. 



1. A. bidentata, Michx. Annual, hirsute, very leafy; leaves mostly 

 alternate, lanceolate, sessile or clasping, entire or with 2 short basal lobes; 

 fruit acute, with 4 short spines. — Northern Mississippi, and westward. — 

 Stem 1^-2° high. 



* * Heads of sterile flowers cup-shaped, toothed. 



2. A. hispida, Pursh. Stem prostrate and shrubby at the base; the 

 branches hir.sute ; leaves bipiiniatifid, thickish ; spikes few, the terminal one 

 elongated ; fruit downy, unarmed. — Sandv shores, South Florida, f(jrming 

 large clusters. 



3. A. artemisiaefolia, L. (rj.\r,wEF.r).) Annual, erect, hairy or 

 smoothish ; leaves bipiiniatifid, with linear lobes; the upper often entire; 

 spikes single or panicled ; fertile flowers single, clustered, or sometimes 

 spiked; fruit nearly globose, armed with si.\ short teeth. (A. elatior. L. 

 A. paniculata, ^fich.v., spines of the fruit obsolete.) — Cultivated ground, 

 everywhere. July - Sept. — Stem 1° - 4° high. 



4. A. triflda, L. Stem tall ( 6° -10°), 4-sided, rough-hairy; leaves rough, 

 palmately 3 -o-lobed, with the lobes ovate-lanceolate and serrate, or all uudi- 



