270 American Midland Naturalist Monograph No. 2 



2. Bracts 8-9, equalling or shorter than the flowers; peduncles scarcely or not 

 at all thickened below the head; roadsides and fields, common; nat. 



from Eur. May-Aug. Yellow Goat's-beard T. pratensis L. 



2. Bracts 10-13, longer than the flowers; peduncles conspicuously thickened 



below the head; waste places, occasional; introd. from Eur. June 



T. diibius Scop. 



1. Flowers purple; bracts longer than the flowers; peduncles thickened below 

 the head; roadsides and fields, occasional; nat. from Eur. June-Aug. Vege- 

 table Oyster T. porrifolius L. 



55. Krigia Schreb. 



(^Adopogon Necker; Cynthia D.Don) 

 1. Plants perennial; pappus of 10-15 minute scales, and 15-20 long bristles. 

 2. Plants with a solitary head on a leafless scape; involucre 10-15 mm. high; 

 plant bearing a small globose tuber; open woods in the s. half of 111., 

 northw. to Fayette Co. Apr. -May. [C. dandelion (L.) DC; A. dande- 

 lion (L.) Ktze] K. dandelion (L.) Nutt. 



2. Plants with 1-3 clasping stem-leaves, and several heads; involucre 8-10 

 mm. high; plant without a tuber; wooded slopes and ridges. May-Sept. 

 [K. amplexicaults Nutt.; C. virgmica (L.) D.Don; A. virginicum (L.) 



Ktze} K. biflora (Walt.) Blake 



1. Plants annual; pappus of 5-7 short rounded scales and an equal number of 

 longer bristles; scapes slender, each with one head; leaves basal; involucre 

 6-8 mm. high; dry soil in fields and open woods, chiefly in the valleys of 

 the Illinois and Wabash rivers. May-July. [_A. carolinianum (Walt.) 

 Britt.] K. yirgmtca (L.) Willd. 



56. CiCHORlUM L. — Chicory 



C. intybus L. Roadsides and fields, common; nat. from Eur. June-Nov. 

 There are occasional white-flowered plants. 



57. Lactuca L. — Lettuce 



1. Achenes filiform-beaked; pappus white; flowers pale yellow. 



2. Heads 6-8-flowered; achenes light brown, 5-7-nerved but not transversely 

 rugulose; leaves pinnatifid (or merely spinulose-denticulate in f. integri- 

 jolia Bogenh.), tending to turn edgewise in a vertical position, the 

 margins and midribs spinulose; stem 30-90 cm. tall; fields, waste places, 



and roadsides, common; nat. from Eur. July-Sept. Prickly Lettuce 



L. scariola L. 



2. Heads 12-20-flowered; achenes dark brown, 1-3-nerved, transversely 

 rugulose; stem 1-3 m. tall; native species. 

 3. Leaves entire to pinnatifid, not spinulose-toothed. 



4. Leaves sinuately pinnatifid, or the upper entire; open woods, and 



roadsides, common. Junc-Aug. Wild Lettuce L. canadensis L. 



4. Leaves all unlobed, lanceolate, entire or denticulate; woods and road- 

 sides. June-Aug. \ L. intcgrijolia Bigel.] L. sagittijolia EH. 



3. Leaves spinulose-toothed, the midvein somewhat setose on the lower 

 surface; prairie soil, rare. July. Wady Petra, Stark Co., V. H. Chase 



