COMPOSITA. (COMPOSITE FAMILY.) 223 
LA 
toothed-margined ; fertile flowers 2-4, the short corolla 5-parted. — Varies with 
smaller and fewer-flowered heads, and the corolla of the fertile flower truncate. 
— Drifting sands along the coast, Florida to North Carolina. Aug. and Sept. 
— Stem 1? -29 high. Leaves 1' long. 
36. AMBROSIA, Tourn. 
Heads moneecious, in racemes or spikes ; the upper ones sterile, nodding ; the 
lower pistillate and fertile. Involucre of the sterile flowers hemispherical, com- 
posed of 7-12 united scales, 5-20-flowered. Receptacle naked or with slender 
chaff. Corolla 5-toothed. Involucre of the fertile flowers 1-flowered, ovoid or 
turbinate, entire, closed, pointed, commonly with a row of tubercles or spines 
near the apex. Corolla and stamens none. Achenia globose or ovoid. Pap- 
pus 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. 
* Leaves undivided or 3 — 5-lobed, opposite : receptacle naked. 
l. A. trifida, L. Stem tall (69 — 109), 4-sided, rough-hairy ; leaves rough, 
palmately 3 - 5-lobed, with the lobes ovate-lanceolate and serrate, or all undi- 
vided ; fruit obovate, 6-toothed around the base of the conically beaked apex, 
clustered. (A. integrifolia, Muhl.) — River-banks and rich soil, Florida and 
northward. Aug. and Sept. CST 
* Leaves pinnately lobed ; the PF e^ mostly alternate: receptacle commonly 
iy. 
2. A. crithmifolia, DC. Stem prostrate and shrubby at the base; the 
branches velvety pubescent ; leaves bipinnatifid, thickish, softly pubescent ; 
spikes few, the terminal one elongated ; fruit downy, unarmed. — Sandy shores 
at Key West, forming large clusters. 
3. A. artemisisefolia, L. Annual, erect, hairy or smoothish ; leaves bi- 
pinnatifid, with linear lobes ; the upper often entire; spikes single or panicled ; 
fertile flowers single, clustered, or sometimes spiked ; fruit nearly globose, armed 
With six short teeth. (A. elatior, Z. A. paniculata, Michx., spines of the fruit 
obsolete.) — Cultivated ground, everywhere. J uly — Sept. — Stem 1°- 4° high. 
. & A. hispida, Pursh. Hispid and hoary throughout ; leaves bipinnatifid, 
with toothed lobes; racemes terminal, somewhat panicled. — South Carolina, 
Catesby. — Stem 1° high. Heads larger than in No. 1. (*) 
37. XANTHIUM, Tourn. COCKLEBUR. 
. Heads moneecious, spiked ; the upper ones many-flowered, sterile, with the 
Seales of the involucre separate, in a single row ; the receptacle oblong, chaffy, 
and the short corolla 5-toothed ; the lower ones fertile, consisting of two pistil- — 
late flowers, enclosed in a 2-celled oblong closed involucre, which is armed — — — 
externally with numerous hooked spines or bristles, and terminated by one — — 
_ © two stout beaks. Corolla filiform. Achenium oblong, solitary in eacl 
| e annual herbs. Leaves alternate, lobed and petioled. 
