898 FLOKA. 



Leaves entire or dentate, none of them pinnatifia. 

 Stem glabrous, or hirsute only toward the base. 



Leaves oblong or oblong-lanceolate; achene longer than the beak. 



6. L. sagitti/olia. 

 Leaves lanceolate; achene about equalling the beak. 3. L. Canadensis, 

 Stem hirsute up into the branches of the inflorescence. 7. L. Steelei. 



Outer bracts gradually shorter; heads 16-20 mm. high; flowers blue. 8. L. pulchella. 



(b) Achenes beakless or with short necks, thickish ; flowers blue. 

 Leaves oblong to ovate, acuminate, dentate. 9. L. villosa. 



Leaves pinnatifid, the terminal segment commonly triangular. 10. L. Floridana. 



* * Pappus brown; flowers blue to white. 11. L. spicata. 



i. Lactuca Scariola L. Prickly Lettuce. (I. F. f. 3537.) Biennial, 

 green and glaucous; stem stiff, leafy, usually paniculately branched, glabrous 

 throughout, or hirsute at the base, 6-20 dm. high. Leaves oblong or oblong- 

 lanceolate, denticulate or pinnatifid, sessile or auriculate-clasping, the lowest some- 

 times 25 cm. long and 7 cm. wide, the upper much smaller; heads 4-8 mm. broad, 

 very numerous in an open panicle; involucre cylindric, its outer bracts about one- 

 third the length of the inner; rays yellow; achenes obovate-oblong, about as long 

 as the filiform beak. In fields and waste places, Me. to S. Dak., N. J., Ga., Neb., 

 Colo, and Kans. Nat. from Europe. Aug-Sept. 



Lactuca sah'gna L., the Willow Lettuce of Europe, similar to L. Scariola, but 

 with runcinate-pinnatifid lower leaves, either spinulose on the midvein or unarmed, has 

 been found in Ohio. 



2. Lactuca Ludoviciana (Nutt.) DC. Western Lettuce. (I. F. f. 3538). 

 Biennial, glabrous throughout, leafy up to inflorescence, paniculately branched, 

 6-15 dm. high. Leaves oblong to ovate-oblong, acute or acutish, 5-10 cm. long, 

 auriculate-clasping, spinulose-denticulate to pinnatifid with spinulose segments; 

 heads 6-10 mm. broad, numerous in an open panicle; involucre cylindric or 

 ovoid-cylindric, glabrous, its bracts successively shorter and broader, the lower 

 ones ovate; rays yellow; achenes oval to obovate, flat. Plains and banks, Iowa, 

 Minn, and S. Dak. to Kans. and Tex. July-Sept. 



3. Lactuca Canadensis L. Wild or Tall Lettuce. Wild Opium. (I. F. 

 f* 3539-) Biennial or annual, glabrous throughout, somewhat glaucous; stem 

 leafy up to the inflorescence, 1-3 m. high, branching above into a narrow panicle. 

 Stem-leaves sessile or auriculate-clasping, 5-20 cm. long, the uppermost smaller, 

 often lanceolate, acuminate and entire, the basal often 3 dm. long, narrowed into' 

 petioles; heads numerous, 4-6 mm. broad; involucre cylindric; rays yellow; 

 achenes oval. In moist, open places, N. S. to the N. W. Terr, south to Ga., Ala., 

 La. and Ark. June-Nov. 



Lactuca Canadensis mont&na Britton. Plant 3-12 dm. high ; leaves all lanceolate 

 and entire ; bracts of the involucre purple or purplish. Mountains, Penn. and N. Y. 



4. Lactuca hirsuta Muhl. Hairy or Red Wood-Lettuce. (I. F. f. 3540.) 

 Similar to the preceding species, but commonly smaller and less leafy; stem 

 3-18 dm. high, naked and paniculately branched above, usually hirsute, at least 

 below. Stem-leaves mostly sessile or auriculate-clasping, 7-17 cm. long, the 

 uppermost sometimes lanceolate and entire, tin- basal petioled; midvein rarer! 

 spinulose; heads numerous, 4-6 mm. broad; involucre glabrous. io-l8mm. high; 

 outer bracts shorter than the inner; rays reddish-yellow or paler; achenes oblong- 

 oval, flat, about the length of the beak. In dry soil, Me. to Ont., Minn., Ala. and 

 Tex. July-Sept. 



5. Lactuca Morssii Robinson. Morss Wild LETTUCE. Similar to the prej 

 Ceding ^ptvie>; '-tern strict, leafy, 1-3 m. tall, somewh at hirsute at the base. Leaves 

 runcinate-pinnatifid, the lower sparingly hirsute beneath along the midrib and 

 cordate-clasping narrowed base, the upper glabrous; involucre shorter than in 

 L, hirsuta: rays blue; achenes oval-lam :eol ate, 3 -ribbed on each face, 4-5 mm. 

 Long, 3-4 times as long as the filiform beak. Along salt meadows, Me. and 

 eastern Mass. to N. Y. 



6. Lactuca sagittifolia Ell. Arrow leaved Lettuce. (I. F. f. 3541-) 

 Biennial; stem glabrous throughout, or hirsute below, leafy nearly up to the 

 usually paniculate inflorescence, 6-l8 dm. high. Leaves entire or denticulate, 

 the lower rarely pinnatifid. sometimes spinulose on the margins, those of the stem 



