144 DISSEMINATION OF SEEDS. 



his home. Sometimes, too, he becomes the unintentional 

 agent in disseminating seeds, as when with the seeds of 

 wheat he introduces those of noxious weeds. 



From the history of the different nations of the world 

 we learn how, by wars and by the frequent migration of 

 tribes, plants were carried from country to country. In 

 Europe, even in modern times, armies have been known 

 to carry grains and cultivated vegetables from one ex- 

 tremity of the continent to the other during the time of 

 wars. Great numbers of new plants have been found in 

 France in the vicinity of places to which the Germans 

 carried food for their horses. 



From the time of the discovery of our own land to the 

 present time, we have been receiving additions to our 

 native plants and freely giving of our own to other na- 

 tions. Among the plants earliest introduced were those 

 useful for food and medicine, such as the various cereals, 

 apples, pears, quinces, etc., Datura, Verbascum, Tanac- 

 elum, Artemisia. Plants useful in the arts were soon 

 added to the number cultivated, while those with beauti- 

 ful flowers or foliage quickly followed, and those remark- 

 able for peculiarities in structure were not omitted from 

 the list of introduced or exotic plants. 



When the introduction of these plants is of recent date, 

 we have no difficulty in tracing the origin, but when such 

 introduction took place a long time ago it is difficult, al- 

 most impossible, to do so, and especially difficult because 

 the number introduced unintentionally is in excess of the 

 number introduced intentionally. 



The common plantain, called by the Indians "the white 

 man's foot," follows the steps of the European. One 

 species has become so extensively naturalized as to have 

 become a nuisance in some sections of the United States. 

 Its seeds are of about the size and weight of those of red 



