236 FOUNDATIONS OF BOTANY 
is short at first but lengthens after flowering. Involucre com- 
posed of a single row of long, erect, inner scales and a set of 
much shorter ones outside and at the base of the former ones. 
Akenes cylindrical or spindle-shaped, with 4-5 rough ribs, the 
apex tapering into a bristle-like beak which bears a short, 
broadly conical tuft of soft white hairs. 
1. T. officinale, Weber. DANpDELION. Outer involucre reflexed ; 
inner involucre closing over the head, after the flowers are withered, 
and remaining shut for some days, then opening and allowing the 
akenes to form a globular head. Root stout, bitter, medicinal. 
Young leaves eaten as a pot-herb (“ greens’’) in spring— the plant 
often cultivated for the leaves by market-gardeners. 
XVII. PYRRHOPAPPUS, DC. 
Annual or biennial; stem erect, leafy below, nearly naked 
above, smooth. Leaves oblong, toothed or pinnatifid. Heads 
large, long-peduncled ; involucre cylindrical or spreading, the 
inner row of bracts erect, united at the base, the outer rows 
shorter and spreading; receptacle naked. Flowers yellow; 
rays truncate, 5-toothed at the apex. Akenes oblong, 5-ribbed, 
narrowed above into a long and slender beak; pappus soft, 
tawny, with a short, soft-hairy ring at the base.* 
1. P. carolinianus, DC. Fartse Danperion. Annual or bien- 
nial; stem glabrous, furrowed, branched above, 2-3 ft. high. Lower 
leaves lanceolate to oblong, entire, toothed or pinnatifid, narrowed 
into a margined petiole, the upper sessile, bract-like, entire. Heads 
few, long-peduncled, peduncles and involucre sometimes finely 
downy; inner bracts calloused at the apex, the outer awl-shaped 
and spreading. Akenes much shorter than the thread-like beak. 
Common in fields.* 
XVIII. LACTUCA, Tourn. 
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 truncate, 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.* 
