72 



-and are usually closed by noon. The seed is about J in. long, tapering 

 to a blunt point, the opposite end having a fringe of minute hairs around 

 the crown. The body of the seed is corrugated. An average plant pro- 

 duces about 3,000 seeds. 



Time of flowering, July- October. 



Time of seeding, August- October. 



Dispersal frequently as an impurity in clover and grass seed. 



Eradication. The method outlined for Canada Thistle may be fol- 

 lowed in eradicating this weed, but the plow may have to be used more 

 frequently than is advisable in combating thistles. 



FIG. 31. 



WILD LETTUCE, SOUTHEEN THISTLE, OR TIUJMPET-MILKWEED 

 (Erroneously called Prickly Lettuce.) 



Lactuca Canadensis (L). 



An annual or biennial plant with a leafy stem, which may attain a 

 height of seven feet. The leaves are deeply lobed, terminating in an 

 acute point, and have stalks or petioles, the lower ones being smaller 

 than those near the top of the stem- The stem branches at its summit 

 into a compound flower-cluster. The flowers are small, yellow in color > 

 and open only a few at a time. The seed is dark brown in color, flat, and 

 oval, with longitudinal ribs and a thread-like beak at the apex, and 

 possesses a small white tuft of hair (Fig. 31, a). 



Time of flowering, June- October. 



Time of seeding, July-October. 



Dispersal chiefly by the wind. 



Eradication. Where there is not much of it, r pull and burn before 

 ripening. Where this cannot be done, use the same method as for Mus- 

 tard (Fig. 15.) 



Closely allied to this plant is the Prickly Lettuce (Lactuca scariola) r 

 but distinguished from it by its leaves, the midrib of which is quite spiny. 

 This variety is somewhat troublesome in pastures, but it can be eradicated 

 by cutting and burning before it seeds, or by following the same method as 

 for Mustard (Fig. 15). 



