272 



CICHORIACEAE. 



[Vol. in. 



Involucre KlaiKiularpubescent: heads nearly i' high. i. S. arvfnsis. 

 Involucre glabrous; heads 6"-8" high. 



Auricles of the leaves acute; achenes striate and transverse!}- wrinkled. 2. 5. oleraceits. 



Auricles rounded; achenes ribbed, not transversely wrinkled. 3. S'. asper. 



I. Sonchus arvensis L. Corn Sow- 

 Thistle. Milk Thistle. (Fig. 3534.) 



Sonclnis ar-jensis I,. Sp. PI. 793. 1753. 



Perennial by deep roots and creeping rootstocks, 

 glabrous; stem leafy below, paniculatcly branched 

 and nearly naked above, 2°-4° high. Lower and 

 basal leaves runcinatepinuatifid, often 12' long, 

 spinulose-dentate, narrowed into short petioles, 

 the upper pinuatifid or entire, lanceolate, clasping; 

 heads several or numerous, corymbose-paniculate, 

 l'-2' broad, bright yellow, very showy; involucre 

 nearly i' high, its bracts as also the peduncles 

 glandular-bristly; achenes oblong, compressed, 

 with about 10 rugose longitudinal ribs. 



In low grounds along salt meadows and streams, New 

 Jersey to Quebec and at Great Salt Lake, Utah, and in 

 fields and along roadsides, Newfoundland to Minnesota. 

 Naturalized from Europe. Native also of .\sia. July- 

 Oct. Called also Dindle, Gutweed, Swine Thistle, 

 Tree Sow-Thistle. 



2. Sonchus oleraceus L. Annual 



Sow-Thistle. Hare's Lettuce. 



(Fig- 3535-) 



Sonchus oleraceus h. Sp. PI. 794. 1753. 



Annual, with fibrous roots; stem leafy be- 

 low, nearly simple, i°-io° high. Basal and 

 lower leaves petioled, lyrate-pinnatifid, 4'- 

 10' long, the terminal segment commonly- 

 large and triangular, the margins denticulate 

 with mucronate or scarcely spiny teeth; up- 

 per leaves pinuatifid, clasping by an auricled 

 or sagittate base, the auricles acute or acum- 

 inate; uppermost leaves ofteu lanceolate and 

 entire; heads several or numerous, pale yel- 

 low, 9"-l5" broad; involucre glabrous, 6"- 

 8" high; achenes flat, longitudinally ribbed 

 and transversely rugose. 



In fields and waste places, a common weed in 

 most cultivated parts of the globe except the ex- 

 treme north. Also in Central and South Amer- 

 ica. Naturalized from Europe. Called also Hare's Colewort or Thistle, Milk-weed, Milk Thistle, 



Milky Tassel, Swinies. The leaves used as a salad 

 and as a pot herb. May-Nov. 



3. Sonchus asper (L.) AH. Spiny or 

 Sharp-fringed Sow-Thistle. (Fig. 3536.) 



Sonchus oleraceus var. asper. L. Sp. PI. 794. 1753. 

 Sonchus asper MX. Fl. Ped. i: 222. 1785. 



Annual, similar to the preceding species; leaves 

 undivided, lobed or sometimes pinuatifid, spinu- 

 lose-dentate to spinulose-denticulate, the lower 

 and basal ones obovate or spatulate, petioled, the 

 upper oblong or lanceolate, clasping by an auri- 

 cled base, the auricles rounded; heads several or 

 numerous, i' broad or less; flowers pale yellow; 

 involucre glabrous, about 6" high; achenes flat, 

 longitudinally ribbed. 



In waste places throughout most of our area and 

 in tropical and South .\merica. Widely distributed 

 as a weed in nearly all cultivated parts of the earth. 

 Naturalized from Europe. May-Nov. 



