THE GRASSLANDS 466 



be found anywhere and capable of supporting a varied 

 and highly successful agriculture. The summers are 

 warm and often hot but, generally speaking, have less 

 rain than in the forested regions. The winters are cold 

 and the ground deeply frozen or snow-covered. It is also 

 a region of strong winds. It is still, however, a matter 

 of controversy as to precisely what are the controUing 

 factors in determining this vegetation type. Trees can 

 and do grow in this region when planted and cared for. 



Fig. 131. — An Extensive View of Prairie, with the blazing star, 

 a composite, in bloom. (F. C. Gates.) 



but they do not naturally invade it with success. Along 

 streams there is usually a fringe of trees or even a strip 

 of forest. These are almost always deciduous and not 

 coniferous forest. Under cultivation it has proved es- 

 pecially fitted for the production of wheat and com and 

 to a lesser extent of other cereals and herbaceous crops, 

 particularly fiber plants. And moreover, just as the food 

 supply and plant cover in nature once supported the im- 

 mense herds of bison and other grazing animals of this 

 region, so now the crops of com, grain, and pasturage, 



