1298 CAKDUACEAE 



radiate, corymbose. Involucres hemispheric or flattened : bracts in several series, ap- 

 pressed. Receptacle flat or convex, naked. Kay- or marginal-flowers pistillate, fruit- 

 producing. Disk-flowers perfect, fruit-producing : corollas tubular. Anthers obtuse and 

 entire at the base, usually blunt at the apex. Stigmas truncate, brush-like. Achenes 3-5- 

 angled, or 5-ribbed, often truncate. Pappus a crown-like border. 



1. Tanacetum vulgare L. Plant acrid-aromatic. Stems 3-10 dm. long, sometimes 

 branched : leaf-blades 0.5-2 dm. long, the divisions linear or oblong, pinnatifid, the seg- 

 ments sharply toothed : heads commonly numerous, in flat-topped corymbs : involucres 

 depressed-hemispheric, 6-8 mm. broad ; bracts oblong to linear-lanceolate : corollas yellow, 

 the marginal ones often with oblique 3-toothed ligules : disk flat : achenes 2 mm. long : 

 pappus-crown 5-toothed. 



In waste places and on roadsides, Nova Scotia and Ontario to Minnesota, Georgia and Missouri. 

 Naturalized from Europe. Summer and fall. TANSY. 



135. ARTEMl'siA L. 



Annual or perennial caulescent herbs, or low shrubs, the foliage usually pubescent, 

 Leaves alternate : blades entire, toothed, laciniate or dissected. Heads relatively small, 

 discoid, often numerous, drooping or erect. Involucres various in shape : bracts in sev- 

 eral series, the inner ones successively longer. Receptacle flat or hemispheric, naked or 

 sometimes pubescent, but never chaffy. Flowers various, sometimes all perfect and fruit- 

 producing, sometimes the marginal pistillate and fruit-producing, the central perfect and 

 sometimes neutral. Anthers entire and obtuse at the base, usually subulate-tipped. Achenes 

 2-ribbed, or striate, each topped by a disk. Pappus wanting. WORMWOOD. MUGWORT. 



Flowers about the center of the disk perfect, but not producing fruit. 

 Herbaceous biennial or perennial plants. 



Leaf-blades pinnately dissected into narrowly linear segments. 1. A. caudata. 



Leaf-blades entire, or those of the basal and lower cauline leaves cleft. 2. A. dracuncul&ides. 



Woody perennial shrub. 3. A. filifolia. 



Flowers about the center of the disk perfect and fruit-producing. 

 Leaves glabrous or sparingly pubescent, green, not t9mentose. 



Leaf-blades 2-3-pmnately divided : ultimate divisions of the panicle lax 



racemes : involucres about 1 mm. high. 4. A. annua. 



Leaf-blades pinnately divided, the segments pinnatifid : ultimate divisions 



of the panicle dense spike-like racemes : involucres about 2 mm. high. 5. A. Uennlf. 

 Leaves densely white-tomentose, at least beneath. 



Leaf-blades 2-pinnatifid or 2-pinnately parted. 6. A. vulgaris. 



Leaf-blades entire or shallowly toothed, or some of those of the lower leaves 



pinnatifid. 



Leaf-blades about equally pale and pubescent on both sides. 7. A. gnaphalodes. 



Leaf-blades green and glabrate on the upper surface. 8. A. Mexicana. 



1. Artemisia caudata Michx. Biennial, glabrous. Stems 5-18 dm. tall, often with 

 ascending branches at the base : leaves numerous ; blades once to thrice pinnately divided, 

 the segments nearly filiform : heads very numerous, about 2 mm. in diameter, in elongated 

 panicles : involucres with the central flowers perfect but not producing fruit ; bracts ovate- 

 oval or broadly oblong. 



In sandy soil, Quebec to Manitoba, Florida and Texas. Summer and fall. 



2. Artemisia dracunculoides Pursh. Perennial, glabrous. Stems 6-12 dm. tall, 

 usually much branched, the branches nearly erect : leaves numerous ; blades narrow, com- 

 monly linear, mostly less than 4 mm. wide, entire, shallowly toothed or some of the lower 

 cauline cleft : heads very numerous, 2-3 mm. in diameter, in ample panicled racemes : in- 

 volucres with the central flowers perfect, but not producing fruit : bracts ovate to broadly 

 oblong, green and scarious-margined. 



On dry plains and prairies, Manitoba and the Northwest Territory to Texas, California and British 

 Columbia. Summer and fall. 



3. Artemisia filifolia Torr. Shrubby, thinly pale-pubescent. Stems 3-8 dm. tall, 

 with rigid, nearly erect branches : leaves numerous, 2-5 cm. long ; blades mainly parted 

 into 3 entire filiform segments usually less than 1 mm. wide, some of the upper leaves un- 

 divided : heads exceedingly numerous, 1-1.5 mm. in diameter in panicled racemes : invo- 

 lucres 3-5-flowered ; bracts densely woolly-canescent. 



On dry plains, South Dakota to Utah and Mexico. Summer and fall. 



4. Artemisia annua L. Annual or biennial, glabrous, very aromatic. Stems 4-10 

 dm. tall, much branched : leaves numerous ; blades twice or thrice pinnately divided, 3-11 

 cm. long, the segments oblong or incised or pinnatifid : panicle-branches ending in loose 

 racemes : heads subglobose, scattered, nodding : involucres about 1 mm. high, with the 

 central flowers perfect and fruit-producing ; bracts mostly oval or ovate. 



In waste places, Ontario to Kansas and Tennessee. Naturalized from Europe. Summer. 



