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. Dandelion. 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. 



XVn. 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, vsdth a short, soft-hairy ring at the base.* 



1. P. carolinianus, DC. False Dandelion. 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.* 



XVm. LACTUCA, Toum. 



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, 6-toothed at. the apex. Akenes- compressed, 

 ribbed, the apex contracted into a slender beak, which ia 

 enlarged into a disk bearing the soft, hairy, white or tawny 

 pappus.* 



