Vol. III.] 



CHICORY FAMILY. 



273 



L. Canadensis. 

 L. hirsuta. 



15. LACTUCA L. Sp. PI. 795. 1753- 

 Tall leafy herbs, with small panicled heads of yellow white or blue flowers, and alter- 

 nate leaves. Involucre cylindric, its bracts imbricated in several series, the outer shorter, or 

 of 1 or 2 series of principal nearly equal inner bracts, and several rows of short outer ones. 

 Receptacle flat, naked. Rays truncate and 5-toothed at the summit. Anthers sagittate at 

 the base. Style-branches mostly slender. Achenes oval, oblong or linear, flat, 3-5-ribbed 

 on each face, narrowed above or contracted into a narrow beak, which is somewhat expanded 

 at the summit into a small disk bearing* the copious soft capillary white or brown pappus- 

 bristles. [The Ancient Latin name, from lac, milk, referring to the milky juice. ] 

 About 95 species, natives of the northern hemisphere. 



-,r Pappus bright white. 

 1. Leaves spiny margined and often with spiny or hispid midribs; flowers yellow. 

 Heads 6-12-flowered: involucre very narrow, 4"-6" high. 1. L. Scariola. 



Heads 12-20-flowered; involucre broader. 



Involucre 8"-q" high; achene about as long as its beak. 2. L. Ludoviciana. 



Involucre 4"-6" high; achene longer than its beak. 5. L. sagittifolia. 



2. Leaves neither spiii3'-margined nor with spiny midribs, 

 (a) Achenes very thin, flat, contracted into filiform or tapering beaks. 

 Outer involucral bracts abruptly shorter than the inner; heads 4" -7" high; flowers yellow. 

 Leaves, or some of them, pinnatifid. 



Plant glabrous throughout, 3-io high. 3. 



Leaves, at least their midribs, hirsute; plant i-6 high. 4. 



Leaves entire or dentate, none of them pinnatifid. 



Leaves oblong or oblong-lanceolate; achene longer than the beak. 5. 



Leaves lanceolate; achene about equalling the beak. 3. 



Outer bracts gradually shorter; heads 8"-io'' high; flowers blue. _ 6. 



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

 Leaves oblong to ovate, acuminate, dentate. 7. L. villosa. 



Leaves pinnatifid, the terminal segment commonly triangular. 8. L. Floridana. 



$f -X- Pappus brown; flowers blue. 9. L. spicata. 



i. Lactuca Scariola L. Prickly- 

 Lettuce. (Fig. 3537-) 



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



Biennial, green and glaucous; stem stiff, leafy, 

 usually paniculately branched, glabrous through- 

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

 oblong or oblong-lanceolate, spinulose-mar- 

 gined, denticulate or pinnatifid, sessile or auricu- 

 late-clasping, the lowest sometimes io / long and 

 3 / wide, the upper much smaller; midrib spinu- 

 lose or hispid; heads 2 // ~4 // broad, 6-12-flowered; 

 very numerous in an open panicle; involucre cyl- 

 indric, \ f/ -\y z " 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, New York and Penn- 

 sylvania to Minnesota and Missouri. A trouble- 

 some weed. Naturalized from Europe. Aug-Sept. 



L. 

 L. 

 L. 



sagittifolia. 

 Catiadensis. 



pulchella. 



2. Lactuca Ludoviciana (Nutt.) DC. 

 Western Lettuce. (Fig. 3538.) 



Sonchus Ludovicianus Nutt. Gen. 2: 125. 1818. 

 Lactuca Ludoviciana DC. Prodr. 7: 141. 1838. 



Biennial, glabrous throughout, leafy up to inflor- 

 escence, paniculately branched,2-5 high. Leaves 

 oblong to ovate-oblong, acute or acutish, 2 / -4 / long, 

 auriculate-clasping, spinulose-denticulate, sinuate- 

 lobed, or pinnatifid with spinulose segments; heads 

 3 // ~5 // broad, numerous in an open panicle, their 

 peduncles bracteolate; involucre cylindric or ovoid- 

 cylindric, glabrous, 8 // -o/ / high, its bracts success- 

 ively shorter and broader, the lower ones ovate; 

 rays yellow; achenes oval to obovate, flat, about the 

 length of their filiform beak; pappus white. 



Plains and banks, Iowa, Minnesota and Dakota to 

 Kansas and Texas. July-Sept. 



18 



