COMPOSITAE (COMPOSITE FAMILY) 597 



5. Lactuca ludoviciana (Nutt.) DC. Prodr. 9: 141. 1838. Biennial, 



glabrous throughout, leafy up to inflorescence, paniculately branched, 6-15 

 m. high: leaves oblong to ovate-oblong, acute or acutish, 5-10 cm. long, 

 auriculate-clasping, spinulose-denticulate to pinnatifid with spinulose seg- 

 ments: heads 6-10 mm. broad, numerous in an open panicle; involucre cy- 

 lindric or ovoid-cylindric, glabrous, the bracts successively shorter and broader, 

 the lower ones ovate: rays yellow: achenes oval to obovate, flat. From Mon- 

 tana and the Dakotas to Texas. 



6. Lactuca pulchella (Pursh) DC. 1. c. 131. Perennial, glabrous, more or 

 less glaucous; stems erect, 3-7 dm. tall, corymbosely paniculate above: leaves 

 5-20 cm. long, numerous, linear to lanceolate, entire, toothed, or pinnatifid, 

 acute or obtuse, those of basal and lower stem leaves sometimes with winged 

 petioles, those of upper stem leaves sessile and partly clasping: peduncles often 

 copiously scaly: involucres 16-20 mm. long; inner bracts linear-lanceolate, 

 acute or obtusish : ligules blue or violet : achenes black, the body rather ellip- 

 tic, ribbed, 4 mm. long, beak shorter than the body. (L. sylvatica A. Nels. 

 Bull. Torr. Bot. Club 26: 486. 1899.) In our range, and northward almost 

 across the continent. 



7. Lactuca graminifolia Michx. Fl. Bor. Am. 2: 85. 1803. Biennial or 

 perennial, glabrous or nearly so, glaucescent; stems erect, 6-15 dm. tall, 

 paniculately branched above: leaf-blades elongated-linear or narrowly linear- 

 lanceolate, 10-40 cm. long, entire or with a few spreading or deflexed lobes; 

 both the entire and pinnatifid types often on the same plant: peduncles often 

 with minute scales: involucres 12-15 mm. high; bracts linear-lanceolate to 

 lanceolate, the inner scarious-margined : ligules purple, blue, or rarely white 

 or yellowish: achenes elliptic or elliptic-oblong, 4-4.5 mm. long, the beak 

 much shorter than the body. In the southeastern part of our range to South 

 Carolina and Texas. 



105. SONCHUS L. Sow THISTLE 



Leafy-stemmed, coarse, succulent herbs, chiefly smooth and glaucous. 

 Heads cymose or umbellate, swollen at base or jug-shaped. Involucral bracts 

 few, thin, with many shorter ones at base; these becoming callous-thickened. 

 Flowers yellow. Achenes obcompressed, ribbed, not beaked. Pappus co- 

 pious, of cottony-white exceedingly soft and fine hairs, mainly falling together. 



Heads large; involucre glandular-pubescent . . . . . 1. S. arvensis. 

 Heads medium-sized; involucre glabrous. 



Leaves prickly toothed; auricles rounded . . . . . 2. S. asper. 



Leaves with soft teeth; auricles acute ....... 3. S. oleraceus. 



1. Sonchus arvensis L. Sp. PI. 793. 1753. Rootstocks creeping; stems 

 5-10 dm. high, naked at summit, bearing few or several and corymbosely 

 paniculate showy heads: leaves runcinate-pinnatifid or some undivided, 

 denticulate-spinulose; the cauline partly clasping at base: peduncles and invo- 

 lucre more or less glandular-bristly; head 20-25 mm. high: achenes oblong, 

 about 10-costate, rugulose on the ribs. This weed, naturalized from Europe, 

 is spreading in our range. 



2. Sonchus asper (L.) Hill, Herb. Brit. 1: 47. 1769. Stem often stout, 

 3-15 dm. high, from an annual root: leaves undivided, lobed, or pinnatifid, 

 spinulose-dentate; the lower spatulate to lanceolate, more or less distinctly 

 petioled; the upper clasping by an auriculate base, the auricles rounded: in- 

 volucre glabrous, about 12 mm. high: achenes smooth, 3-nerved on each side. 

 Common in fields and waste places; naturalized from Europe. 



3. Sonchus oleraceus L. Sp. PI. 794. 1753. Fibrous-rooted annual; stem 

 nearly simple, 5-20 dm. high: lower leaves petioled, lyrate-pinnatifid, 1-2 dm. 

 long, the terminal segment commonly large and triangular, the margins den- 

 ticulate with mucronate or scarcely spiny teeth; the upper pinnatifid, clasp- 

 ing by an auriculate or sagittate base, the auricles acute: involucre 12-16 mm. 

 high: achenes flat, longitudinally ribbed and transversely rugose. Common 

 in fields and waste places; naturalized from Europe. 



