252 KEY AND FLORA 



Heads numerous ; involucre glabrous. Akenes flattened, margined, 

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



XIX. LACTUCA L. 



Annual, biennial, or perennial ; stems leafy. Leaves entire 

 to pinnately cut. Heads panicled ; involucre cylindrical ; bracts 

 unequal, overlapping in 2 or more rows, the outer shorter ; 

 receptacle naked. -Flowers blue, yellow, or white ; rays trun- 

 cate, 5-toothed at the apex. Akenes compressed, ribbed, the 

 apex contracted into a slender beak, which is enlarged into a 

 disk bearing the soft, hairy, white or tawny pappus.* 



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, 3-6 ft. high. Leaves ovate to lanceo- 

 late, taper-pointed, often hairy beneath; the lower on winged petioles 

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

 gent and bracted peduncles ; flowers blue. Akenes slightly com- 

 pressed, beak very short ; pappus white. In waste places.* 



XX. AGOSERIS Raf. 



Herbs, usually appearing sternless. Basal leaves tufted, 

 usually sessile. Head solitary, large, yellow or rarely purple, 

 on a naked or bracted scape ; bracts of the involucre ove'rlap- 

 ping in 2 or 3 rows ; receptacle flat, naked or pitted. Akenes 

 smooth, 10-ribbed, with or without a beak; pappus of abundant 

 slender white bristles. 



B. FL species 1 (Nothocalais). 



1. A. cuspidate Steud. Scape 1 ft. or more high. Leaves lanceolate, 

 taper-pointed, woolly-margined. Involucral scales lanceolate, sharp- 

 pointed. Akenes beakless. Prairies and plains W. 



2. A. glauca Steud. Scape stout, 1-2 ft. high. Leaves varying 

 from linear to oblong, entire, dentate or pinnately cut. Heads 1-2 

 in. in diameter. Akenes beaked. Plains W. 



