360 COMPOSITAE. 



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

 short-beaked. 



In moist ground, in open woods, and on banks. 



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 tegules 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 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, glab- 

 rous, 12-14 mm. long, the outer tegules successively shorter, all lanceolate, 

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

 beaked; pappus copious, white. 



Vancouver, Washington; rare in our limits. 



496. SONCHUS. Sow THISTLE. 



Leafy-stemmed mostly glabrous generally coarse herbs, with 

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

 tegules 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. 



Heads large; involucre glandular-pubescent. 5. arvensis. 

 Heads medium-sized; involucre glabrous. 



Leaves prickly-toothed; auricles rounded. S. asper. 



Leaves with soft teeth; auricles acute. S. oleraceus. 



Sonchus arvensis L. Perennial, glabrous to the inflorescence; stems 60-100 

 cm. high, erect; lower leaves oblanceolate in outline, runcinately lobed, spinu- 

 lose-denticulate, petioled, 10-30 cm. long, the upper lanceolate, clasping at 

 base; heads 3-5 cm. broad; involucre glandular; ligulate corollas bright yellow; 

 akenes longitudinally ribbed. 



A weed, sparingly introduced from Europe. 



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

 cous, glabrous below, glandular above ; lower leaves ovate or broadly spatulate, 

 obtuse or acute, rarely lobed, spinulose-dentate, the petioles margined; 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. 



A common weed, introduced from Europe. 



Sonchus oleraceus L. Annual, glabrous, pale green; stems usually 60-90 

 cm. high, erect, simple or but little branched; leaves pinnately cleft or parted, 

 10-20 cm. long, the terminal segment large, triangular, denticulate, the lateral 

 lobes much smaller; lower leaves petioled, the upper auriculate-clasping; 

 involucre cylindric, glabrous; akenes flat, marked with longitudinal and 

 cross ribs. 



A weed, introduced from Europe. 



