244 COMPOSITE. (COMPOSITE FAMILY.) 



6-12-flowered; scales of the involucre 4-5, obovate, ciliate; fertile flowers 

 1-3. Dry barren soil, Florida to South Carolina. August -Sept. Stem 

 l-2high. 



3. I. ciliata, Willd. Annual, hispid ; stem branching ; leaves ovate, 

 acuminate, coarsely serrate ; spikes dense, the bracts elongated ; scales of the 

 involucre 3-4, roundish, ciliate; fertile flowers mostly 3. Mississippi 

 (Carpenter), and westward. Sept. Stem 2 -3 high. Leaves 3' -4' long. 



* * Scales of the involucre 6-9, imbricated in 2-4 rows. 



4. I. imbricata, Walt. Somewhat shrubby, smooth; leaves fleshy, 

 lanceolate, the lower ones slightly serrate and 3-ribbed, the upper alternate 

 and entire ; heads many-flowered ; outer scales of the involucre orbicular ; 

 the inner obovate, 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. August- Sept. Stem l-2 high. Leaves 1' long. 



42. AMBROSIA, Tourn. 



Heads monoecious, in racemes or spikes ; the upper ones sterile, nodding ; 

 the lower pistillate and fertile. Involucre of the sterile flowers composed 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 turbi- 

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

 the apex. Corolla and stamens none. Achenia globose or ovoid. Pappus 

 none. Herbs. Leaves mostly piuuately 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 densely spiked, the top-shaped involucre produced on 

 one side into a long recurved appendage: fertile heads axil/art/, 4-aiujled. 



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 l-2 high. 



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



2. A. hispida, 1'ursh. Stem prostrate and shrubby at the base; the 

 branches hirsute; leaves bipinnatifid, thickish ; spikes few, the terminal one 

 elongated; fruit downy, unarmed. Sandy shores, South Florida, forming 

 large clusters. 



3. A. artemisisefolia, L. (RAGWEED.) Annual, erect, hairy or 

 smoothish ; leaves bipinnatifid, 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. L. 

 A. paniculata, Michx., spines of the fruit obsolete.) Cultivated ground, 

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



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

 palmately 3 -5-lobed, with the lobes ovate-lanceolate and serrate, or all uudi- 



