APPLICATIONS OF BOTANY 



249 



national forest reserves, comprising 174,261,393 acres of land, 

 and employs 3500 men. Most of the states also own forest re- 

 serves and employ professional foresters, and many cities also 

 employ professional foresters to look after their park and 

 street trees. 



Plant breeding works for the improvement of existing vari- 

 eties and the production of new varieties. Previous to the reoog- 



Fia. 114. — Denuded of forest growth by ruthless cutting and fires. A barren rocky wa«te is 

 left, unsuited to other agricultural crops. (U. S. D. A.) 



iiition of the work of Mendel and DeVries, it consisted almost 

 entirely in the aimless selection of desirable individuals and the 

 progress was alow. However, the great majority of our valuable 

 agricultural varieties were . probably obtained in this manner. 

 The ultimate object of plant breeding is to increase the yield, 

 improve the quality of the product, to secure new varieties, or to 

 develop resistance to drouth or disease. It involves selection, 

 hybridization and a thorough knowledge of the Taws of evolu- 



