3'S 



CICHORIACEAE 



VOL. III. 



Leaves glabrous. 



Leaves entire to pinnatifid, not sagittate at base. 

 Leaves entire or denticulate, sagittate at base. 



6. L. canadensis. 

 j. L. sagittifolia. 



B. Achenes truncate, or narrowed into stout beaks; rays blue to white. 



Perennial ; achenes flattened. 

 Annuals or biennials ; achenes swollen. 

 Pappus bright white. 



Achenes beakless ; leaves dentate, acuminate. 

 Achenes beaked ; leaves pinnatifid. 

 Pappus brown ; achenes short-beaked. 



8. L.pulchella. 



9. L. villosa. 



10. L. floridana. 



11. L. spicata. 



i. Lactuca virosa L. Prickly or Wild 

 Lettuce. Fig. 4068. 



Lactuca virosa L. Sp. PI. 795. 1753. 

 Lactuca Serriola L. Cent. PI. 2: 29. 1756. 

 Lactuca Scariola L. Sp. PI. Ed. 2, 1119. 1763. 



Biennial, green and glaucous ; stem stiff, leafy, 

 usually paniculately branched, glabrous through- 

 out, or bristly-hirsute at the base, 2-7 high. 

 Leaves oblong or oblong-lanceolate, spinulose- 

 margined, denticulate or pinnatifid, sessile or 

 auriculate-clasping, the lowest sometimes 10' 

 long and 3' wide, the upper much smaller; 

 midrib spinulose or hispid; heads 2"-4" broad, 

 6-i2-flowered ; very numerous in an open pan- 

 icle; involucre cylindric, i"-i$" thick, its outer 

 bracts about one-third the length of the inner; 

 rays yellow; achenes obovate-oblong, about as 

 long as the filiform beak; pappus white. 



In fields and waste places, Vermont to Georgia, 

 west to the Pacific Coast. A troublesome weed. 

 Naturalized from Europe. Consists of several 

 races, differing in the form, lobing and position of the leaves. Aug.-Sept. Milk- or horse-thistle. 



2. Lactuca saligna L. Willow Let- 

 tuce. Fig. 4069. 



Lactuca saligna L. Sp. PI. 796. 1753. 



Biennial, light green ; stem slender, smooth 

 or nearly so, 2 high or more, the very 

 slender branches erect-ascending. Leaves 

 glabrous, linear to oblong, 6' long or less, 

 runcinate-pinnatifid with pointed divergent 

 lobes, or entire, sagittate at the base, the 

 midvein sometimes spinulose ; panicles nar- 

 row ; heads about 3" broad, few-flowered ; 

 involucre subcylindric; outer bracts much 

 shorter than the inner; achenes oblong, 

 about one-half as long as the filiform beak; 

 pappus white. 



Waste and cultivated grounds, Ohio, 

 uralized from Europe. July-Aug. 



Nat- 



