DESCRIPTIONS OF SOME COMMON WEEDS 



253 



states and occasionally in Wisconsin, Illinois, Iowa and 

 Utah. Abundant in Manitoba and Ontario. 



Annual Sow Thistle (Sonchus oleraceus, L.) Annual 

 or perennial succulent herb with leafy stem, smooth and 

 glaucus ; corymbed or umbellate heads of yellow flowers ; 

 stem leaves dentate, runci- 

 nate-pinnatifid, terminal seg- 

 ments large and triangular; 

 heads numerous; flowers pale 

 yellow, occurring in summer 

 and autumn. Common in 

 fields and waste places 

 throughout North America, 

 especially far northward ; also 

 from Mexico to South Arrier- 



ica. 



The Spiny-leaved Sow 

 Thistle (Sonchus asper, (L.) 

 Hill.) is nearly like common 

 sow thistle; but has lower 

 stem-leaves less divided and 

 more spiny toothed. 



Prickly Lettuce (Lactuca 

 scariola, L.). A tall, erect 

 annual or winter annual, 

 glaucus, green, two to six FIg . l6l . Prickly lettuce (Lac . 

 feet high, simple or branched tuca scariola). (C. M. King.) 

 except on the lower part of 



the stem which has stiff bristles ; leaves smooth except on 

 the midrib where there are weak prickles; lanceolate to 

 oblong in outline, with spiny toothed margin, occasion- 

 ally wavy toothed, base arrow-shaped, clasping the stem ; 

 leaves becoming vertical by a twist (in shady places 

 leaves not twisted) ; flowers in small heads on open pani- 

 cles, each head bearing from four to fourteen yellow 

 flowers; achenes flat, nerved, prolonged into a long, fili- 



