552 



COMPOSITAE (COMPOSITE FAMILY} 



FIG. 382. Smooth White 

 Lettuce (Prenanthes ' racemosa). 

 X*. 



in each head ; involucre cylindric, 

 with eight to ten linear bracts in its 

 principal row, with a few short, 

 spreading outer ones. Achenes 

 small, slender, with fine, straw-col- 

 ored pappus. 



Means of control 



Cut flower-stalks close to the 

 ground before the buds unfold, thus 

 preventing seed development and 

 distribution. Drainage and cultiva- 

 tion of the soil are necessary in order 

 to kill the perennial roots. 



ROUGH WHITE LETTUCE 



Prendnthes dspera, Michx. 

 (Ndbalus dsper, T. & G.) 



Native. Perennial. Propagates by 

 seed. 



Time of bloom : August to Septem- 

 ber. 



Seed-time : September to October. 



Range : Ohio to South Dakota, south- 

 ward to Kentucky, Kansas, and 

 Louisiana. 



Habitat : Dry prairies ; fields, pas- 

 tures, waste places. 



Grazing cattle usually leave this weed undisturbed to perfect 

 its fruit, liking neither its rough-hairy foliage nor its bitter juices. 

 Stem stout, simple, ridged, and bristly-hairy, two to four feet tall. 

 Leaves long-oval or broadly lance-shaped, rather thick and firm, 

 rough on both sides, sparsely toothed, obtuse, the basal ones taper- 

 ing to winged petioles ; those on the stem all sessile, the lower ones 

 clasping and obtuse, the uppermost usually entire and acute. 

 Heads numerous, in a long, spike-like panicle, mostly erect on very 

 short pedicels, each about a half-inch broad, with twelve to fifteen 

 cream-colored florets ; involucre cylindric, very hairy, its principal 



