COMPOSITAE. 249 



370. LACTUCA. WILD LETTUCE. 



Leafy-stemmed herbs, with milky juice; flowers yellow or blue 

 or whitish, in paniculate few to many-flowered heads; bracts of 

 the involucre in 2-few rows, the outer shorter; receptacle flat, 

 naked; pappus of copious very short and fine capillary bristles 

 which are not plumose; corollas all ligulate; akenes flat or 

 flattish, narrowed at the summit or beaked. 



Pappus brown; flowers whitish. L. spicala. 

 Pappus white; flowers not whitish. 



Flowers yellow; leaves spiny. L. scariola. 



Flowers blue; leaves not spiny. L. pulchella. 



Lactuca spicata (Lam.) Hitchc. Biennial, erect, 1-3 m. high, glabrous 

 or nearly so, pale green, very leafy; leaves coarsely pinnatifid, the lobes ir- 

 regularly toothed, the uppermost sessile and sometimes clasping; heads in a 

 long narrow panicle; involucre 10 mm. high; flowers bluish to whitish; akenes 

 short-beaked. In moist ground, in open woods. 



Lactuca scariola integrata Gren. & Godr. Prickly Lettuce. Annual or 

 biennial, erect, 1-2 m. high, glabrous and somewhat glaucous; leaves oblong 

 or lanceolate, spiny on the margin and midrib, entire or irregularly toothed or 

 cleft, sessile and usually auriculate-clasping at base, 5-20 cm. long, the upper- 

 most, much reduced; heads in large loose panicles; involucre narrowly cylindric, 

 glabrous, 10-12 mm. long, the outer bracts much shorter than the inner ones; 

 flowers yellow; akenes flattened, narrowed into a beak longer than the body, 

 as long as the bright white pappus. A troublesome weed, introduced from 

 Europe. 



Lactuca pulchella (Pursh) DC. Blue-flowered Lettuce. Perennial, erect, 

 leafy, 30-90 cm. high, puberulent or glabrate; leaves lanceolate, tapering at 

 each end, acute or cuspidate, entire or sinuately toothed or lobed, 5-15 cm. 

 long; lower leaves petioled; heads loosely panicled; involucre cylindric, 

 glabrous, 12-14 mm. long, the outer bracts successively shorter, all lanceolate, 

 acute; flowers blue or violet; akenes flat, not margined, 4 mm. long, very short 

 beaked; pappus copious, white. Locally abundant. A very troublesome weed 

 in some sections. 



371. SONCHUS. Sow THISTLE. 



Leafy-stemmed mostly glabrous generally coarse herbs, with 

 milky juice; flowers yellow, in corymbose or paniculate heads; 

 bracts of the involucre imbricated, the outer shorter; receptacle 

 flat, naked; pappus of copious very fine and short capillary 

 bristles, which are not plumose; corollas all ligulate; akenes flat 

 or flattish, truncate, not beaked. 



Sonchus asper (L.) Hill. Annual, erect, 30-90 cm. high, somewhat 

 glaucous, glabrous below, glandular, above; lower leaves ovate or broadly 

 spatulate, obtuse or acute, rarely lobed, spinulose-dentate, the petioles mar- 

 gined; upper leaves oblong or oval, sessile and clasping at base, acuminate; 

 heads cymosely arranged; involucre cylindric-campanulate, about 1 cm. broad, 

 glabrous; flowers yellow; akenes flat, margined, 3-nerved on each side. Spar- 

 ingly introduced. 



