Jones: Flora of Illinois, 152. Compositae 271 



743; without locality, Vasey. Western Lettuce 



L. ludoviciana (Nutt.) DC. 



1 . Achenes not filiform-beaked. 

 5. Pappus white; flowers blue. 



6. Leaves oval, coarsely and unevenly dentate; achenes 4 mm. long; 



woods, throughout 111., except the n.w. counties. Aug. -Sept 



L. vtllosa Jacq. 



6. Leaves lyrate-pinnatifid, the terminal segment larger, triangular; achenes 



5-6 mm. long; woods. July -Sept L. jloridana (L.) Gaertn. 



5. Pappus brown; flowers cream or bluish; leaves pinnatifid or merely sinu- 

 ate; alluvial soil in woods, common. Aug.-Sept. [L. spicata of auth.} 

 L. biennis (Moench) Fern. 



58. SoNCHUS L. — Sow-thisde 



1. Plants perennial, with rhizomes; heads 4-5 cm. in diameter, the flowers bright 

 yellow; involucre 1.5 cm. high; achenes 2.5-3 mm. long, striate and papil- 

 lose; fields and waste places; nat. from Eur. July-Sept. Field Sow-thistle 



S. arvensis L. 



1. Plants annual; heads 1-2.5 cm. in diameter, pale yellow; involucre 1 cm. 

 high; achenes 2-2.5 mm. long. 

 2. Leaves runcinate-pinnatifid, scarcely prickly, the terminal segment com- 

 monly large and triangular; upper leaves clasping by an acute, sagittate 

 base; achenes longitudinally striate and papillose; fields and waste 

 places; nat. from Eur. June-Nov. Common Sow-thistle ...S. oleraceus L. 

 2. Leaves toothed or more or less curled or lobed, harshly prickly, the basal 

 auricles rounded; achenes longitudinally ribbed, otherwise smooth; 

 fields and waste places; nat. from Eur. May-Aug. Spiny Sow-thistle 

 S. asper (L.) Hill 



59. Prenanthes L. 



(^Nabalus Cass.) 

 1. Involucre glabrous. 



2. Heads 5-7-flowered; pappus straw-colored; plants not glaucous; oak 

 woods, local; apparently absent from the w. part of the state. Aug.- 

 Sept P. altissima L. 



2. Heads 8-12-flowered; pappus reddish brown; plants glaucous; woods, n. 



111., southw. to Peoria Co. Aug.-Sept P. alba L. 



1. Involucre pubescent. 



3. Heads 12-16-flowered; basal leaves oblanceolate. 



4. Stem glabrous; upper leaves clasping; flowers purplish; moist ground, 



throughout 111., except the s.w. part. Aug.-Sept 



P. racemosa Michx. 



4. Stem hirsute; leaves not clasping; flowers cream; prairie soil. Aug.-Sept. 

 P. aspera Michx. 



3. Heads 20-3 5 -flowered; basal leaves deltoid; stem glabrous or puberulent; 

 flowers cream; banks of streams, locally throughout 111., but apparently 

 absent from the n. counties. Aug. -Oct P. crepidinea Michx. 



