174 FARM WEEDS OF CANADA 



PRICKXY LETTUCE (Lactuca scariola L., var. integrata Gren. 



& Godr.) 



Other English names : Compass Plant or Weed Milk Thistle. 



Other Latin name : Lactuca virosa of American authors not L, 



Introduced from Europe. Annual, occasionally a winter 

 annual. A coarse, tall-stemmed plant, averaging 3 to 5 feet in 

 height. In British Columbia plants 8 feet high have been found. 

 The leaves are oblong-lance-shaped margined with spines and 

 prickly on the midrib beneath, only the lower ones more or less 

 pinnatifid, stalkless, with ear-like lobes at the base. The leaves 

 of the stem are twisted at the clasping base so as to stand vertically 

 with the edge to the sun, instead of horizontally, as in the case 

 of the leaves of most plants. This peculiarity has given rise 

 to a common name of this lettuce, the Compass Plant. The 

 flower heads are pale yellow, less than 1/2 inch across, on a large, 

 wide-spreading panicle, only a few open at a time. 



The seed (Plate 76, fig. 97) is about 1/8 inchlong, dark greenish- 

 gray, similar to that of the black-seeded varieties of the garden 

 lettuce, usually a little smaller, and, like them, broadly lance- 

 shaped and somewhat curved, flattened, margined and bearing 

 5 to 7 narrow ridges down each face; whole surface roughened 

 with fine wrinkles, and short, white bristles on the ridges near 

 the apex. The beak widens at the apex and is as long as the 

 seed, very slender and often twisted; pappus white. Both 

 beak and pappus easily broken off by handling the seed. 



Time of flowering: July-August; seeds ripe by August. 



Propagation: By seeds, which are carried long distances 

 by the wind. 



Occurrence : Widely distributed in waste places from Nova 

 Scotia to the Prairie Provinces and reported from parts of British 

 Columbia ; sometimes giving trouble in fields. The seed is 

 frequently found among crop seeds. 



