DICOTYLEDONOUS PLANTS 237 



1. L. canadensis, L. WILD LETTUCE. Biennial ; stem erect, 

 smooth, hollow, branched above, 3-10 ft. high. Leaves lanceolate 

 to spatulate, pale beneath, the lower petioled and pinnately cut, the 

 upper sessile, clasping, and nearly entire. Heads numerous, about 

 20-flowered. Flowers yellow ; akenes oval, flat, 1-ribbed on each 

 side, minutely roughened, about as long as the beak. Pappus 

 white. In waste places.* 



2. L. acuminata, Gray. BLUE LETTUCE. Stem very leafy, 

 smooth, paniculately branched above, 36 ft. high. Leaves ovate to 

 lanceolate, taper-pointed, often hairy beneath, the lower on winged 

 petioles and often sinuate-lobed, the upper sessile. Heads racemed, 

 on divergent and bracted peduncles. Flowers blue. Akenes slightly 

 compressed, beak very short. Pappus white. In waste places.* 



XIX. SONCHUS, L. 



Annual or perennial. Leaves mostly toothed or pinnately 

 cut, prickly margined. Heads in corymbs or panicles ; bracts 

 in several series, the outer shorter ; receptacle naked. Flowers 

 yellow, rays truncate, 5-toothed at the apex. Akenes oval to 

 oblong, compressed, ribbed, truncate at the apex. Pappus of 

 numerous soft white hairs.* 



1. S. oleraceus, L. Sow THISTLE. Annual; stem erect, branched, 

 smooth, 2-6 ft. high. Leaves spiny-toothed, the lower long-petioled, 

 very irregularly cut or pinnatifid, the upper clasping by an eared 

 base. Involucre downy when young. Akenes channeled and trans- 

 versely wrinkled. In waste places on very rich soil.* 



2. S. asper, Vill. SPINY Sow THISTLE. Annual; stem erect, 

 smooth, branched but little, 2-6 ft. high. Leaves undivided, spatu- 

 late to oblanceolate, fringed with spiny teeth, the lower narrowed 

 into a petiole, the upper clasping by an eared base, the ears rounded. 

 Heads numerous ; involucre glabrous. Akenes flattened, margined, 

 3-nerved on each side, smooth. In waste places.* 



