DISSEMINATION OF SEEDS. 145 



clover and, when once mixed with the latter, cannot be 

 readily separated, and hence in cultivating the clover the 

 plantain is disseminated. 



Chickweed, called by the New England savage " the 

 mark of the pale face," is a native of Europe, but is now 

 found in nearly all parts of the world. 



Some of our most troublesome weeds have been brought 

 to us from Europe. Cirsium arvense, Onopordum Acan- 

 thium, and Lappa officinalis, better known, perhaps, by 

 the names, Canada thistle, cotton thistle, and burdock, 

 are very common examples of such plants. Taraxacum 

 dens-leonis, the common dandelion, too, is a foreign plant, 

 not very disagreeable, but so thoroughly naturalized as to 

 be more abundant than welcome in some pastures and 

 meadows. Whiteweed, called now by the more eupho- 

 nious name, Marguerites, is another intruder which has 

 obtained exclusive possession of some fields. 



Soil raised to the surface in the digging for railway 

 cuttings and embankments is often covered with a growth 

 of plants, strangers in the locality. These sometimes sur- 

 vive a few years and then disappear as the natural vege- 

 tation of the section gains strength and kills the intruder; 

 at other times, the new plants continue to flourish. 



By commerce, the most pernicious weeds have spread 

 from Europe to America and India where they have 

 made themselves at home sometimes by their wonderful 

 vitality usurping the place of the native plants. White- 

 weed and woadwax, Leucanthemum and Genista, two of 

 the greatest pests of Essex County, were thus introduced. 



From the West in 1855, Rudbeckia hirta was brought 

 in hay seed to New England and now bids fair to usurp 

 a place in our fields that should be occupied by useful 

 plants. 



Seeds are often found in the fleeces of wool carried 



