SOME BACTERIAL DISEASES OF PLANTS. 119 



curing of tobacco, the souring of milk, the tanning of leather, etc., 

 are dependent upon the action of bacteria. They are at the very 

 foundation of agriculture, being one of the chief natural factors in 

 the production and maintenance of soil fertility. They are the 

 most efficient scavengers of the earth, breaking down and disinte- 

 grating with incredible rapidity the dead plants and animals of the 

 earth, reducing their complex substances to simple ones which 

 again become available as building materials in the ever recurring 

 cycle of growth and decay. 



History of our Knowledge of Bacterial Diseases of 



Plants. 



While we usually think of bacteria as producers of disease in 

 man and other animals yet we are coming rapidly to the realization 

 of their importance as related to many of the diseases of our culti- 

 vated plants. About 1880 Dr. Burrill of the Illinois Experiment 

 Station discovered bacteria in the tissues of apple and pear trees 

 affected with Fire Blight. In 1884, Dr. J. C. Arthur now of the 

 Indiana Experiment Station but then of the New York (Geneva) 

 Experiment Station showed by careful inoculation experiments 

 that the bacteria discovered by Dr. Burrill were the responsible 

 agents in causing the disease known as Fire or Pear Blight. In 

 1897 Russell and Harding of Wisconsin Experiment Station and 

 E. F. Smith of the U. S. Department of Agriculture working inde- 

 pendently established the bacterial nature of the Black Rot of 

 cabbage. Following these came Stewart and Harding of New 

 York who have added very materially to our knowledge of the Black 

 Rot germ. Jones of Vermont and Harrison of Canada have done 

 classical work on the Soft Rots of vegetables. There are besides 

 these many others both in this and other countries who are adding 

 every year to our knowledge of the bacterial diseases of plants. 

 The whole subject is now being worked over and the scattered 

 facts brought together by Dr. E. F. Smith of the U. S. Department 

 of Agriculture. The first volume of his monograph entitled "Bac- 

 teria in Relation to Plant Diseases" has already appeared as a 

 publication of the Carnegie Institution. It promises to be a land- 

 mark in this particular branch of economic science. 



