THE CROWN GALL CONTROVERSY. 251 



Fruit Tree Bark Beetle, Bulletin No. 44, Agricultural Experi- 

 ment Station, Columbia, Mo. 



Common Apple Tree Borer, Bull. 44, Agriculture Exp. Station, 

 Columbia, Mo. 



Apple Insects, Bull. 56, Agriculture Exp. Station, Orona, Me. 

 Apple Bud Borer, Bull. 53, Agri. Exp. Station, Newark, Del. 

 Fruit Tree Bark Borer, Bull. 53, Agri. Exp. Sta., 

 Periodical Cicade, Bull. 53, Agri. Exp. Station, " " 



Codling Moth, " 64, " " " Logan, Utah. 



Ribbed Cocoon Maker, Bull. 214, Agri. Exp. Sta., Ithaca, N. Y. 

 Woolly Aphis, Circular 20, U. S., Department of Agriculture, 

 Washington. 



Insect Enemies of the Apple Tree, Bruner, State Horticultural 

 Society Report 1894. 



Insect Enemies of the Apple Tree and Fruit, Bruner, State 

 Horticultural Society, Report 1899. 



The last two references cover nearly all the known insect 

 enemies of the apple tree, and in many cases no other refer- 

 ences need be consulted. 



THE CROWN GALL CONTROVERSY. 



BY F. E. DENNY, LINCOLN. 



Since about 1892 when attention was first directed to the 

 disease called crown gall, a great deal has been written upon 

 the subject. Except in a few cases these opinions were not the 

 result of careful, scientific experiments, but were more in the 

 form of speculations upon the reports of others. The literature 

 upon crown gall has therefore become a mass of conflicting 

 testimony, so conflicting in fact that upon almost every point 

 authorities differ. The object of this paper is to show in what 

 a dissatisfactory state the crown gall problem is in at the pre- 

 sent time, and to indicate to the reader what statements in 

 regard to this much-talked-of disease may be believed, and 

 what statements may reasonably be doubted. 



