WEEDS. 299 



seeds to bury themselves in the soil. They often 

 cause flock-owners much trouble by burying them- 

 selves in the flesh of their sheep. 



By artificial means of dissemination are meant those 

 in which man is concerned. 



Weeds have been introduced by being grown for 

 ornamental purposes, such as butter and eggs {Linaria 

 vulgaris)^ and velvet leaf (Abutilen avicennae). Others 

 have escaped from cultivation, such as parsnip and 

 mustard. From being plants in place they have be- 

 come plants out of place. 



Common carriers are a soui'ce of weed distribution. 

 Weeds and other seeds have followed the pioneer step 

 by step along the lines of common travel. The pro- 

 gress of many plants have been traced along these 

 thoroughfares. Useful plants have also been distrib- 

 uted. Thus Kentucky blue grass is known to have 

 been introduced into one locality of Northern Illinois 

 by the night camping of the pioneer. When first in- 

 troduced it was thought to be a harmful weed which 

 would ruin the country. 



Weed seeds are brought from the Eastern hemis- 

 phere by the ballast which ships bring in their west- 

 ern trips. The packing of marble shipped from Ver- 

 mont has been known to bring Canada thistle seeds to 

 Illinois. In honoring the dead the trials of the living 

 have been increased. The army weed {Amarantiis 

 spinosos) is so called in Ohio because it was intro- 

 duced into that state during the civil war. 



Impure seed is a common source of weed distribu- 

 tion, and one that may in a great measure be avoided. 

 Clover and grass seeds are. a frequent source of trouble. 

 Canada thistle, ox-eye daisy, and bearded plantain are 



