242 IOWA ACADEMY OF SCIENCE Vol. XXVI, li)i;i 



Leaves pinnatifid, spinulose-denticulate L. scariosa 



Heads 12 to 20 flowered, akenes oval to oval-oblong, blackish, 

 1 nerved on each face with narrow margins. 



Tall, 4 to 10 feet high, leaves 4 to 15 inches long, 



sinuate, pinnatifid. flowers pale yellow.. L. caiiadcns s 



Leaves thickish, strictly entire L. sagittifolia 



Stem more uniformly leafy, basal bracts somewhat 

 foliacious, lobes of leaves spinulose-toothed, flow- 

 ers in our plant light purple... L. ludov'.clana 



2 Section, Lactucastrum, A. Gray, Akenes flat, marginless, 



beak slender, pappus white, perennial.. L. pulchcUa 



3 Section, Mulgedium (Cass) A. Gray. Akenes thickish, oblong; 

 beak or neck almost wanting, annual or biennial ; flowers niosLiy 

 blue. 



Pappus white, akenes beakless, curved L. villosa 



Pappus tawny, neck short L. spicata 



1. Lactiica virosa L. Sp. Plant. 795. ( 1753.) 



L. scariola intcgrata Auct. Am. L. inicgrata Aven Nelson, 

 Prickly Lettuce. 



Green and glaucous, stems paniculate branched, two to six feet 

 high, scabrous or hirsute at base ; leaves mostly entire with spinulose 

 denticulate margins, the .midrib usually spiny ; margins of the leaves 

 more frequently retaining a horizontal position than the following. 

 Bases sessile or auriculate-clasping, the lower frequently six to 

 ten inches long and two to three inches wide. Heads four to six 

 lines high and two to four lines broad, six to twelve flowered, very 

 numerous, the outer bracts shorter, rays yellow ; akenes linear- 

 oblong, or ovate-oblong, somewhat shorter than the wavy, filiform 

 beak ; pappus copious, wdiite. This plant is reported to be poisonous 

 to young geese, and Mr. Fred Fitzpatrick of Iowa City says that 

 young goslings pasture on it in preference to any other plant and 

 that he once deliberately experimented by allowing a number of 

 goslings to feed on it. all of which died as a result. This, like the 

 following, being an annual, may be easily controlled by not allow- 

 ing it to ripen seed, but the laws regarding the mowing of weeds 

 must be more rigidly enforced if these pests are to be kept in sub- 

 jection. The seeds have mostly been introduced as impurities in 

 ckner, millet and heavier grass seeds. Doctor Pammel in his Weed 

 h^lora, pp. 396-399, gives illustrations and interesting notes regard- 

 ing this and the following species, and in Rhodora for October, 1918, 

 p. 180, is an article from his pen giving additional information re- 



