HISTORY AND SCOPE OF PLANT PATHOLOGY 155 



classical work on the morphology and biology of the fungi, pub- 

 lished in 1884 at Leipzig, and three years later issued in the English 

 language. 



Beside great progress made in mycology during the thirty-year 

 period now under consideration, another subject was started and 

 well advanced, which was to become one of the most important sci- 

 ences affecting pathology, whether of plants or animals, and destined 

 to exert the greatest influence, furthermore, upon human well-being. 

 Pasteur had prepared the way by his epoch-making researches on 

 wine and beer, and the diseases of silkworms, for many excursions 

 into the new world of the "infinitely little," the mighty pigmy 

 kingdom of the bacteria, discovered by Leeuwenhock a century 

 before, but almost unrecognized until now. It had been shown 

 that bacteria were plants, although their power of rapid movement 

 kept many students from fully accepting the fact, when, at the 

 beginning of this period, Cohn, the distinguished botanist of Bres- 

 lau, first systematized the flora of this new realm, and established 

 the infant science of bacteriology. Already Koch, then a young 

 physician practicing in the vicinity of Breslau, had placed the 

 question of the bacterial origin of certain contagious diseases of 

 animals beyond doubt by his studies of anthrax, but it was not 

 until the last of the period that any plant disease was definitely 

 shown to have a similar origin. In 1880 Dr. Burrill, of the Uni- 

 versity of Illinois, published his studies on pear-blight, which he 

 called the anthrax of trees, demonstrating that it was always 

 accompanied by an enormous production of minute, colorless bac- 

 teria, and that the disease could be set up in perfectly healthy trees 

 by inoculating a few of these bacteria into the young shoots. As 

 in the case of every important discovery, it required subsequent 

 studies fully to establish the claims of the discoverer, and to pro- 

 cure popular acceptance of the truth. Even to-day, after the lapse of 

 a quarter of a century, there appears to be a lurking suspicion in the 

 minds of most European botanists that, after all, the bacteria ac- 

 companying pear-blight are not, strictly speaking, the cause of this 

 destructive disease of pomaceous trees. This is doubtless in part 

 due to the fact that the disease does not occur in Europe and other 

 countries outside of North America, for which our trans-Atlantic 

 fruit-growers have reason to be profoundly grateful, although prob- 

 ably unaware of their good fortune. If our distinguished botanical 

 visitors from across the waters to this Congress will observe the 

 great injury which the disease has produced this year in American 

 orchards, in many places killing outright a majority of the pear- 

 trees, and doing immense harm to apple- and quince-trees, and will 

 let it be known upon their return that the statements regarding 

 this disease are not boastful tales to be classed as characteristic 



