194 COMPOSITJE. 



%. Stem 1 3 feet high, erect, branched ; heads in a rather large terminal 

 corymb ; rays 8 12, white, roundish, 3-toothed ; disk white. When dried and 

 pulverized the plant has been employed to excite sneezing, whence its common 

 name. Introduced from Europe. Common Sneezewort. 



42. ACHILLEA. Linn. Yarrow. 



(So named because its healing virtues were said to have been first discovered 

 by Achilles.) 



Heads many-flowered ; the ray flowers 4 6 pistillate, ligu- 

 late, short, or none ; those of the disk perfect, tubular, 5- 

 toothed. Involucre ovate-oblong, the scales imbricate. Re- 

 ceptacle small, usually flat, chaffy. Achenia oblong, smooth, 

 somewhat compressed, margined. Pappus none. 



A. Millefolium Linn. : stem erect, somewhat hairy, sulcate : leaves bi- 

 pinnate, slightly hairy ; the lobes linear, toothed, mucronate. 



Fields and woods. Arct. Amer. to Flor. W. to Oregon and Mexico. June 

 Aug. %.. Stem 2 3 feet high, branched at the top. Leaves 2 6 inches long, 

 cut into very numerous narrow segments. Heads numerous, in a dense terminal 

 fastigiate corymb ; rays about 5, white or rose-colored. It is sometimes em- 

 ployed as a tonic and astringent. Introduced and extensively naturalized. 



Common Yarrow or Milfoil. 



43. LEUCANTHEMUM. Twrn. Ox-eye Daisy. 



(From the Greek ACVKOJ, white, and avQt^ov, a flower.) 



Heads many-flowered ; the ray-flowers numerous, pistillate, or 

 rarely neutral ; those of the disk perfect, with a fleshy somewhat 

 two-winged tube. Involucre broad, imbricate ; the scales with 

 a somewhat scarious margin. Receptacle naked, flat, or con- 

 vex. Achenia of the ray always without pappus ; of the disk 

 sometimes with a short pappus. 



L. vulgare Lam. : stem erect, somewhat branched ; lower leaves petiolate, 

 obovate, toothed; cauline somewhat clasping, serrate, incisely serrate at 

 base ; scales of the involucre with a narrow brownish margin. Chrysanthe- 

 mum Leucanthemum Linn. 



Fields arfd road sides. Can. and throughout the U. S. June Aug. 1\.. 

 Stem 1 2 feet high, erect or subdecumbent at base, smoothish. Leaves often 

 pinnatifid-toothed near the base. Heads large, solitary on the branches ; rays 

 20 30, white; disk' flowers numerous, yellow. Introduced, and everywhere, 

 naturalized . A very troublesome weed. Large Ox-eye Daisy, 



44. ARTEMISIA. Linn. Wormwood. 

 Named from Artem's, the Diana of the Greeks.) 



Heads discoid, few- or many -flowered ; the outer flowers in 

 one series, often pistillate, 3-toothed, with a long exsert bifid 

 style ; those of the disk 5-toothed, perfect, sterile or staminate 

 by abortion of the ovary. Involucre imbricate ; the scales dry 



