86 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



duced into this country, probably first into Canada and from tlience 

 into the United States. 



The Canada thistle nearly or quite fails to seed in many localities, 

 spreading chiefly by the running root-stocks, so that it is not very 

 rapidly disseminated. The failure to seed is doubtless mainly due to 

 its dioecious character, as, if completely so, no seed would be formed 

 where a jDatch originated from a single plant. It is not yet trouble- 

 some to any extent beyond the Eastern and Middle States. It prefers 

 a heavy soil, but on such land is most easily killed. In pastures, or 

 wherever the land is compact, if only a few plants apjDear they may 

 often be killed by pulling them up a few times. Larger patches should 

 be plowed deeply about once a week in the growing season, or each 

 time before any plants appear above the surface. After each plowing 

 rolling is advantageous, especially on sandy soil. There are numer- 

 ous instances where fields of this weed have been completely killed in 

 a single season in time to sow winter wheat. Cases have been re- 

 ported of Canada thistles being killed by a single cutting at a certain 

 period of growth. In some of these instances at least the plant has 

 proved to be some other thistle. If the characters above given are 

 borne in mind, especially the fact of the creeping root-stocks and of 

 its growing on dry land, there will be little danger of this mistake. 



Plate VI, Fig. 1. a portion of the stem, leaves, and flower-heads; 

 Fig. 2, a portion of the running root-stock; Fig. 3, a single flower, 

 with the seed and pappus. 



Arctium Lappa (burdock). 



A well-known biennial plant of the natural order Compositce, 

 which, like many of our common weeds, has been introduced from 

 Europe. It has a thick branching stem, 3 to 5 feet high, with round- 

 ish heart-shaped leaves 3 inches to a foot or more long, the lowest on 

 long stout stalks, the upper ones nearly sessile, the margins undulate 

 and sometimes erosely toothed. The flower-heads are roundish, about 

 an inch thick, mostly in small clusters at the ends of the branches. 

 The scales of the involucre are extended into hooked points, which 

 adhere to the clothing or to the hair or wool of animals. Within the 

 involucre are a number of slender purplish flowers, each containing 

 anthers and styles of the kind peculiar to this order, and at the base 

 of each flower is the seed, surmounted with a number of slender 

 bristles. 



There are several varieties of this species, differing in the size of the 

 heads and in other points, which varieties are by some called ' ' species. '"' 

 It gives but little trouble in cultivated land, being found in waste 

 places about buildings and fences, and occasionally in meadows where 

 the seeding is thin. It prefers strong soil, and its presence is consid- 

 ered a sign of good land. Though not a serious weed in cultivated 

 crops, its unsightliness and the annoyance of its burs in the wool and 

 hair of animals make it desirable to try to exterminate it, especially 

 as it is one of the easiest weeds to get rid of. One of the best times 

 to destroy it is in the fall when the leaves are conspicuous and time is 

 less pressing. It is killed any time if cut below the crown. It may 

 also be killed by being mowed when the seed has fully formed, and 

 the tops burned. If cut while in flower, as somictimes recommended, 

 a second crop of seed will generally be produced. 



Burdock has some reputation in medicine as a blood purifier and for 

 rheumatism. Its value is probably slight. It is known in England as 

 hare-burs or hurrburr, and the young shoots, after being stripped of 



