400 Keport of the Department of Horticulture of the 



is it possible to cause immunity in plants by vaccinations, inocula- 

 tions or injections. 



Inherited immunity is possessed by animals and plants alike. 

 Negroes are immune to yellow fever; some cattle and sheep to 

 anthrax ; certain pears and apples are immune to blight ; some 

 peaches to leaf-curl. Immunity sometimes belongs to species, 

 sometimes to races or varieties and sometimes to individuals. 



But while we are in comparative ignorance of how immunity is 

 transmitted w T e now have a substantial body of facts showing that 

 it can be bred in plants. As far back as 1900, in the medieval 

 days, almost the prehistoric days, of plant breeding, as we view the 

 progress that has since been made, the breeding of disease-resistant 

 plants had been begun and has been steadily carried on since 

 through selection and by crossing. Through selection Blinn l has 

 developed a cantaloupe resistant to blight ; Bolley 2 has bred a flax 

 resistant to flax wilt ; Bain and Essary 3 a red clover that with- 

 stands a fungus ; Jones 4 has selected a potato resistant to late 

 blight ; and Orton 5 has grown a cowpea resistant to a wait fungus. 

 The work done with these plants should be most suggestive to 

 breeders of apples. 



Not so much has been done through hybridizing but still a very 

 promising start has been made. Orton 6 has grown a hybrid be- 

 tween the watermelon and the citron which is resistant to the 

 watermelon wilt, while Biffen "' has made the most important dis- 



1 Blinn, P. K. A rust-resisting cantaloupe. Colo. Agr. Exp. Sta. Bull. 

 104. N 1905. 



2 Bolley, H. L. Breeding for resistance or immunity to disease. Proc. 

 Amer. Breeders' Assoc. 1: 131-135. 1905. 



3 Bain, S. M., and Essary, S. H. Selection for disease-resistant clover. 

 Tenn. Agr. Exp. Sta. Bull. 75. D 1906. 



4 Jones, L. K. Disease resistance of potatoes. U. S. Dept. Agr. PI. Ind. 

 Bull. 87. 1905. 



5 Orton, W. A. The wilt disease of the cowpea and its control. U. S. Dept. 

 Agr. PI. Ind. Bull. 17: 9-22. 1902. 



6 Orton, W. A. A study of disease resistance in watermelons. Science II. 

 25: 228. 1907. 



i Biffen, K. H. Mendel's laws of inheritance and wheat breeding. Jour. 

 Agr. Sci. 1: 4-48. 1905. 



. Studies in the inheritance of disease resistance. Jour. Agr. Sci. 



2: 109-128. Ap. 1907. 



