1906.] 



Some Common Thistles. 



711 



are produced. The stems and leaves, both of seedlings and 

 mature plants, are very sensitive to frost. The first frosts of 

 November and December kill off all the green parts above 

 ground, but the buds on the roots below are uninjured, and 

 it is from these that the plant is chiefly propagated. 



Methods for the Extermination of Thistles. — The 

 methods adopted for the destruction of thistles, if they are to be 



Fig. 6.— Root of Young Marsh Thistle. 



of any use, must take into consideration the life-history of the 

 plant. There is an old well-known rhyme which runs some- 

 what thus — 



" Cut thistles in May 

 They'll grow the next day, 

 Cut 'em in June 

 They'll come again soon, 

 Cut in July 

 They'll surely die.'' 



Now this advice to leave cutting until July is excellent so far 



