340 ELEMENTARY STUDIES IN BOTANY 



44. Selection for regions. One important fact con- 

 nected with plant-breeding needs to be emphasized. The 

 natural tendency is for cultivators of plants to attempt to 

 grow the same kinds of plants everywhere. If natural vege- 

 tation is observed, it will be observed that the assemblages 

 of plants, technically known as the " plant population," 

 differ in different regions, which means that nature does not 

 attempt to grow the same plants everywhere. It is obvious 

 that for every region there is the most suitable group of culti- 

 vated plants, that is, plants that will do the best. If this is 

 considered, each region can be made to yield its maximum 

 of plant products, which would greatly increase the total 

 production of a large country like the United States. 



45. The food problem. The food problem is one of the 

 most important problems of this country. It has become a 

 problem because the rate of increase of population is much 

 larger than the rate of increase of food production. It is 

 evident that this inequality of the two rates must not be 

 allowed to continue indefinitely. The recent developments 

 in plant-breeding, indicated in the preceding paragraphs, 

 together with the increase of knowledge in reference to the 

 nature of the soil and its manipulation, outlined in Chapter 

 III, make it possible to multiply many times the plant prod- 

 ucts of the country. This becomes evident if the following 

 possibilities are realized : 



1 . Securing plants of largest yield and most desirable qual- 

 ity through the various methods of plant-breeding. 



2. Securing disease-resistant races, by means of which 

 frequent and great loss in plant products can be prevented. 



3. Securing drought-resistant races, by means of which 

 crops can not only be insured against drought where they are 

 grown now, but their cultivation can be extended into new 

 regions, especially those which have been regarded as too dry 

 for such plants. 



4. Selection for each region of the group of cultivated 



