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. Witp Letruce. 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. Biur 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 stemless. Basal leaves tufted, 
usually sessile. Head solitary, large, yellow or rarely purple, 
on a naked or bracted scape ; bracts of the involucre overlap- 
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. cuspidata 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. 
