68 HANDBOOK OF NATURE STUDY 



31. Review and Summary. 



MATERIAL : A piece of soil with its natural sod ; a piece of field 

 soil with the stubble or grain plants. 



Most of the wild plants growing in our country are natives 

 of this continent. The first settlers found them growing wild 

 as we find them to-day. Among cultivated plants, Indian 

 corn and tobacco are also natives of North America, and 

 were to some extent cultivated by the Indians. 



Nearly all our other cultivated plants were brought from 

 Europe when this continent was settled by white people. 

 With the seeds of useful plants, nearly all the noxious Euro- 

 pean weeds have been introduced on our farms, and some of 

 them, like the Russian thistle, have spread with amazing 

 rapidity. Do you know of injurious animals which have 

 been introduced into this country ? 



Cultivation has brought about very great changes in this 

 country and especially in the surface of the soil. Millions of 

 acres, indeed whole states that formerly were dense forest 

 or wild prairie, have been converted into farms and gardens. 

 The ploughed and manured land is good soil, not only for wheat 

 and other grain, but also for a host of iveeds. These seed them- 

 selves, and man tills the ground for them unintentionally. In 

 a wild country, such plants as the ragweeds and the false 

 sunflower, which grow best on loose and bare soil, have to 

 be content with the little ground which is laid bare or de- 

 posited by water runs, streams, and burrowing animals, 

 such as gophers, skunks, rabbits, etc. ; but when that wild 

 country is settled, an unlimited acreage of ground is pre- 

 pared for these weeds on farms, in gardens, and on roads and 

 railways. Of this favorable ground our native weeds quickly 

 possess themselves, and their relations, introduced in vari- 

 ous ways, were not slow to claim a share. 



The fact that some farmers have more land than they can 



