DISCUSSION OF PLANT INDUSTEIES 451 



study is now being made regarding the nature of these limit- 

 ing factors. The Rothamsted experiment and hundreds of 

 others that have been made in the United States show the 

 good effects upon soil fertility that may be secured by proper 

 rotation of crops and proper care of the soil. 



II. SPECIAL CARE OF PLANTS 



413. Horticulture and gardening. Scientific study has aided 

 much not only in the matter of the better growth and care of 

 field crops and the forests, but in gardening and agriculture 

 as well. All that has been said about what a plant is and how 

 it lives, and about soils, cultivation, and plant food, applies in 

 some way to gardening and agriculture ; it must be recognized, 

 moreover, that each garden or orchard crop is a specialty in 

 itself, and requires special study for mastery. Almost every 

 kind of garden or orchard plant thrives and yields best in cer- 

 tain climates, in certain kinds of soils, often with certain kinds 

 of exposure to light; has its own peculiar diseases, and re- 

 quires particular treatment in caring for its matured product. 

 It can be no part of this general discussion of botany to deal 

 with such matters in detail, but two or three kinds of special 

 care should be discussed as illustrations of the nature of the 

 work that is being done. 



414. Pruning. In Sect. 60, Chapter IV, there was a discus- 

 sion of the way ia which natural pruning occurs. Artificial 

 pruning has become a general practice, and the botanical 

 relations of the process are therefore significant. 



In injured plants, whose branches have been broken by wind 

 or other destructive agencies, cutting away the broken parts 

 discontinues the passage of food into the injured portions, 

 makes it possible for new branches to grow into the space 

 occupied by the injured branches, and decreases the danger of 

 disease infection. Often the last result is not secured because 

 the cut area is not treated so as to prevent entrance of fungus 

 spores, bacteria, or insect parasites. When the wound that is 



