264 American Midland Naturalist Monograph No. 7 



41. Helenium L. — Sneezeweed 



1. Leaves lanceolate to elliptical, more or less decurrent on the angular 

 stem; rays 1-2 cm long; plants perennial. 

 2. Disk yellow; leaves lanceolate or oblanceolate, mostly dentate; 

 ray-flowers fertile; low meadows, and along ditches, streams, 

 and ponds, common. Aug.-Oct. [H. latifolium Mill.; H. 



canaliculatum Lam.; H. altissimum Link ex Rydb.] 



H. autuninale L. 



2. Disk brownish-purple; leaves linear-lanceolate, mostly entire; 

 ray-flowers neutral, often brownish-purple at base; roadsides, 

 meadows, and pastures, more common in the southern half 

 of the state, but extending northward to Adams and Ver- 

 milion counties. June-Sept. [H. polyphyllum Small] 



H. nudiflorum Nutt. 



1. Leaves narrowly linear, numerous, entire, not decurrent; rays 

 6-10 mm long; disk yellow; plants annual; dry ground, s. 111., 

 often abundant, extending northw. to Pike Co. Aug.-Oct. 

 Bitterweed H. tenuijolium Nutt. 



42. Dyssodia Cav. — Dogweed 

 D. papposa (Vent.) Hitchc. Roadsides and fields, not common. 

 Sept.-Oct. [D. chrysanthemoides (Willd.) Lag.]. 



43. Achillea L. — Yarrow. Milfoil 



1. Leaves and stems green, thinly villous; ultimate leaf-segments 

 lanceolate; corymb flat-topped, up to 30 cm broad; roadsides, 

 fields, lawns, etc., very common; nat. from Eur. May-Aug. 



Rays sometimes pink. [A. occidentalis Raf.] 



A. millefolium L. 



1. Leaves and stems copiously grayish villous-tomentose; ultimate 

 leaf-segments crowded, linear; coiymb strongly convex, 2-8 

 cm broad; roadsides and fields, occasional; adv. from w. U.S. 

 June-Aug - A. lanulosa Nutt. 



44. Anthemis L. 

 I.Rays 10-18, white; achenes not flattened. 



2. Chaff of the receptacle subulate, stiff, subtending only the 

 inner flowers; rays neuter; achenes sparsely glandular- 

 tuberculate, 1-1.5 mm long; plants annual, ill-scented when 

 fresh; fields and waste places, common; nat. from Eur. May- 

 Sept. Dog-fennel or Mayweed [Maruta cotula (L.) DC] 



A. cotula L. 



2. Chaff membranous or absent; rays fertile. 



3. Chaff broad, obtuse, or absent; achenes obtusely 3-angled, 

 1-1.5 mm long; plants perennial, tomentulose, pleasantly 

 aromatic; cultivated, and occasionally spontaneous; introd. 



from Eur. June-Aug. Garden Chamomile 



A. nobilis L. 



