266 American Midland Naturalist Monograph No. 2 



41. Matricaria L. 



M. matricarioides (Less.) Porter. Pineapple-weed. Roadsides, farmyards, 

 and waste places, not uncommon; adv. or nat. from the Pacific Coast. May- 

 Aug. \_M. suaveoleris (Pursh) Buch.} 



42. Chrysanthemum L. 



1. Heads 3-5 cm. broad, few or solitary; rays 20-30; fields, roadsides, and waste 

 places, common; nat. from Eur. May- Aug. [Leucanthemu?n vulgare 

 Lam.; C. leiicanthemuni var. pinnatifidum Lecoq. & Lamotte} Ox-eye 

 Daisy C. leucanthemiun L. 



L Heads 5-15 mm. broad, corymbose; rays 10-15, or absent; waste places, es- 

 caped from cult.; nat. from Eur. Sept. -Oct. [Balsamita inajor Desf.; C. 

 balsamita var. tanacetoides Boiss.} C. balsamita L. 



43. Tanacetum L. — Tansy 

 T. vulgare L. Waste places, escaped from cult.,, nat. from Eur. July-Sept. 



44. Artemisia L. — Wormwood 

 1. Leaves or their divisions linear to filiform, glabrous, or nearly so, green. 

 2. Bracts of the involucre glabrous; heads 2-3 mm. broad; disk-flowers sterile. 

 3. Leaves simple, all entire, or the lower trifid; plants perennial; prairie 



soil, rare. July-Sept. Lee Co., Vasey [A. cernua Nutt.} 



A. dracunculoides Pursh 



3. Leaves 1-3-pinnately divided; plants biennial; sandy soil in the n. part 



of the state, local. July-Sept A. caudata Michx. 



2. Bracts tomentulose; heads 3-4 mm. broad; disk-flowers fertile; leaves 1-3- 

 pinnately parted; plants perennial, shrubby, often cult., and sometimes 



persisting; introd. from Eur. Aug. -Sept. Southernwood 



A. abrotanum L. 



1. Leaves or their divisions lanceolate to linear. 



4. Plants more or less whitish-tomentose; perennials. 

 5. Leaves lanceolate or the uper linear. 



6. Leaves regularly serrate, lanceolate, acuminate, green above, whitish- 

 tomentose beneath; alluvial soil in the n. half of the state, rare. 

 Aug.-Sept A. serrata Nutt. 



6. Leaves entire or few-toothed, tomentose on both sides, but usually 



less so above; along railroads and river banks; adv. from w.- 



centr. U.S. Aug.-Sept. [A. ludoviciana of auth., not Nutt.] 



A. gnaphalode^ Nutt. 



5. Leaves all pinnatifid. 



7. Leaves green and glabrate above, the lobes acute; heads 3-4 mm. 



high; receptacle glabrous; waste places, occasional; escaped from 



cult.; introd. from Eur. July-Oct A. vulgaris L. 



7. Leaves canescent on both sides, the lobes obtuse; heads very numer- 

 ous, about 2 mm. high; receptacle glabrous; roadsides and waste 

 places, occasional; escaped from cult.; introd. from Eur. July-Sept. 

 Common Wormwood or Absinth A. absinthium L. 



